Scotland Independence: Can Scotland, Wales and Northern Ireland Legally Leave the UK?

Introduction

On September 14, 2026, John Swinney, Rhun ap Iorwerth and Michelle O’Neill are due to meet in Cardiff in their capacities as party leaders and sign a memorandum calling for Westminster to facilitate constitutional change in Scotland, Wales and Northern Ireland (McKernan and Greenfield, 2026). The renewed debate over Scotland’s independence is consequently being joined to two other constitutional questions that do not rest on the same legal foundations. International law does not give all three nations a common unilateral right to leave the United Kingdom, and UK constitutional law does not provide them with identical routes to a referendum or change of status.

Scotland illustrates the distinction between political support for independence and legal authority to initiate the process. The 2014 referendum proceeded after an Order under section 30 of the Scotland Act 1998 modified the reserved-matters framework for that specific vote (Scotland Act 1998 (Modification of Schedule 5) Order 2013). In 2022, the UK Supreme Court held that the Scottish Parliament could not legislate for another independence referendum under its existing competence because the proposed Bill related to reserved matters concerning the Union and the Parliament of the United Kingdom (UK Supreme Court, 2022). Wales has no corresponding referendum mechanism: the union of Wales and England and the UK Parliament are reserved matters under Schedule 7A to the Government of Wales Act 2006.

Northern Ireland stands on a different legal footing. The Belfast/Good Friday Agreement recognizes that its constitutional status rests on the principle of consent, while section 1 and Schedule 1 of the Northern Ireland Act 1998 provide a statutory procedure through which a majority may choose to leave the United Kingdom and form part of a united Ireland (Belfast Agreement, 1998; Northern Ireland Act 1998). This is not a general right of unilateral secession. It is a specific constitutional mechanism created through the 1998 settlement and implemented in UK law.

International law supplies a broader framework but does not erase these domestic distinctions. Article 1(2) of the UN Charter identifies respect for the principle of equal rights and self-determination of peoples as one of the purposes of the United Nations (United Nations, 1945). Common Article 1 of the International Covenant on Civil and Political Rights and the International Covenant on Economic, Social and Cultural Rights states that all peoples have the right of self-determination and may freely determine their political status (United Nations, 1966a; United Nations, 1966b). The clearest applications of external self-determination have arisen in contexts such as decolonization and foreign domination, rather than as a general entitlement of territorial communities within existing democratic states to create new states unilaterally.

The International Court of Justice’s Kosovo advisory opinion did not establish such an entitlement. The Court held that Kosovo’s 2008 declaration of independence did not violate international law, while expressly declining to decide whether international law conferred a positive right to secede (ICJ, 2010). The separate doctrine sometimes described as remedial secession remains contested and has generally been argued in connection with exceptional circumstances involving severe oppression or the denial of meaningful internal self-determination. The UK Supreme Court concluded in 2022 that the international-law arguments advanced in that context did not provide Scotland with a right to secede unilaterally. No comparable judicial ruling has established such a right for Wales.

The legal significance of the Cardiff initiative lies in the contrast between a shared political claim and three different constitutional positions. Self-determination, legislative authority to hold a referendum, and a legal entitlement to secede are separate questions. Lawful constitutional change remains possible in each case, but Scotland and Wales presently depend on processes involving the UK constitutional order, while Northern Ireland already has a consent-based mechanism governing the possibility of Irish unity. That distinction is essential to understanding what claims of a “right to decide” mean in legal rather than purely political terms.

1. The Cardiff Summit and the Claim of a Right to Decide

The Cardiff meeting places three constitutional movements under a shared political claim without giving them a shared legal mechanism. John Swinney, Rhun ap Iorwerth and Michelle O’Neill are expected to endorse a memorandum calling on Westminster to facilitate constitutional change in Scotland, Wales and Northern Ireland. The meeting is taking place in their capacities as party leaders rather than as representatives concluding an agreement on behalf of the three devolved governments (The Guardian, 2026).

That distinction limits the memorandum’s legal effect. A political agreement among party leaders cannot amend the Scotland Act 1998, the Government of Wales Act 2006 or the Northern Ireland Act 1998, nor can it reallocate legislative authority between Westminster and the devolved institutions. Its significance lies instead in the coordinated political assertion that constitutional status should ultimately depend on democratic choice.

The same distinction applies in international law. A political memorandum among parties is not an international treaty between states within the meaning of the Vienna Convention on the Law of Treaties. Nor can a declaration by sub-state political actors, without the requisite state practice and acceptance as law, establish a new rule of customary international law (Vienna Convention on the Law of Treaties, 1969; International Law Commission, 2018).

As of September 13, 2026, the final text of the memorandum had not been made public. Its precise language may affect the political claims made in Cardiff, but it cannot remove the central legal difference among the three cases. Scotland, Wales and Northern Ireland may advance a common argument about democratic choice while remaining subject to distinct constitutional arrangements governing how such a choice could acquire legal effect.

2. Self-Determination Is Not a General Right to Secede

Self-determination occupies an established place in international law. Article 1(2) of the UN Charter identifies respect for the principle of equal rights and self-determination of peoples among the purposes of the United Nations. Common Article 1 of the International Covenant on Civil and Political Rights and the International Covenant on Economic, Social and Cultural Rights provides that all peoples have the right of self-determination and may freely determine their political status and pursue their economic, social and cultural development (United Nations, 1945; United Nations, 1966a; United Nations, 1966b).

Those provisions do not prescribe independence as the necessary outcome of every claim to self-determination. The right may operate within an existing state through representative government, political participation and forms of territorial autonomy. In other legal and historical contexts, most clearly decolonization, it has supported the creation of independent states.

It is also unnecessary to resolve conclusively whether the Scots, the Welsh or the population of Northern Ireland constitute a “people” for every purpose of international law. Even if that status is assumed, a separate question remains: whether self-determination gives the population concerned a legal entitlement to leave an existing democratic state unilaterally. International law does not treat those propositions as synonymous.

2.1 Internal and External Self-Determination

The distinction between internal and external self-determination is central to that inquiry. Internal self-determination concerns the ability of a population to participate meaningfully in its government and pursue its political, economic, social and cultural development within the existing state. Representative institutions and territorial autonomy are among the arrangements through which that right may be exercised.

Scotland and Wales each possess elected legislatures and governments exercising extensive devolved powers. Northern Ireland has a different constitutional structure based on devolution, power sharing and the arrangements established following the 1998 peace settlement. These institutions do not eliminate political demands for Scottish or Welsh independence or Irish unity, but they are relevant when claims to external self-determination are assessed.

The clearest international legal application of external self-determination arose during decolonization. General Assembly Resolution 1514 (XV) declared the right of colonial peoples to independence, and the International Court of Justice subsequently treated self-determination as legally central to the status of non-self-governing territories in the Western Sahara and Chagos advisory opinions (United Nations General Assembly, 1960; ICJ, 1975; ICJ, 2019).

Those authorities do not convert every internal constitutional dispute into a decolonization question. The legal regimes governing non-self-governing territories developed in response to colonial domination and cannot simply be transferred to Scotland or Wales because independence movements exist there.

Statehood can nevertheless emerge outside the colonial setting. Secession may occur through constitutional procedures, political agreement or negotiated separation, and international law can accommodate a new state once the relevant legal and factual conditions are satisfied. The absence of a colonial entitlement to independence does not make agreed separation unlawful; it means that the general law of self-determination does not itself supply an unrestricted unilateral right to achieve it.

2.2 Territorial Integrity and Remedial Secession

The Friendly Relations Declaration of 1970 provides an influential formulation of the relationship between self-determination and territorial integrity. It recognizes several possible modes through which a people may determine its political status, including the establishment of an independent state, while also protecting the territorial integrity or political unity of sovereign states that conduct themselves consistently with equal rights and self-determination and possess representative government (United Nations General Assembly, 1970).

Resolution 2625 (XXV) is a General Assembly resolution rather than a treaty and is not binding merely by virtue of its adoption. Its importance lies in its authoritative formulation of principles that have repeatedly informed international legal reasoning, including the principles of self-determination, non-intervention and territorial integrity. The status of particular propositions within the Declaration must still be assessed according to the ordinary sources of international law.

Territorial integrity also does not operate as a straightforward prohibition directed at every internal independence movement. In the Kosovo advisory opinion, the International Court of Justice observed that the principle of territorial integrity, as reflected in the Charter and related international instruments, concerns relations between states (ICJ, 2010). That conclusion does not itself create a right of secession for sub-state entities.

A more controversial issue is the doctrine commonly described as remedial secession. Some legal arguments maintain that severe oppression or a sustained denial of meaningful internal self-determination may, in exceptional circumstances, support a claim to external self-determination. The Supreme Court of Canada acknowledged the possibility of such an exceptional claim in the Quebec Secession Reference without recognizing a general entitlement to unilateral secession (Supreme Court of Canada, 1998).

The doctrine remains unsettled at the international level. States participating in the Kosovo proceedings advanced sharply different positions on whether remedial secession exists as a rule of international law and what conditions, if any, would activate it. The ICJ did not resolve that disagreement because the question before it concerned the legality of Kosovo’s declaration of independence rather than the existence of a positive right to secede (ICJ, 2010).

For Scotland, the issue has received direct judicial consideration. In 2022, the UK Supreme Court relied on the reasoning of the Canadian Supreme Court and concluded that the exceptional circumstances discussed in the Quebec case did not apply to Scotland. International self-determination consequently did not provide Scotland with a unilateral legal entitlement to secede from the United Kingdom (UK Supreme Court, 2022).

No corresponding judgment has decided the international-law position of Wales. The circumstances generally invoked in arguments for external self-determination—colonial rule, alien domination, foreign occupation or exclusion from meaningful political participation—do not correspond to Wales’s present constitutional position. That is an application of the existing doctrine to the Welsh context, not a judicial holding specifically concerning Welsh independence.

Northern Ireland follows a different legal logic. The possibility of leaving the United Kingdom does not depend on proving a right of remedial secession. It rests on the consent-based constitutional arrangements established through the 1998 settlement and given effect in domestic law.

2.3 Kosovo Did Not Create a General Right to Secede

The Kosovo advisory opinion is often invoked in debates over independence, but the International Court of Justice answered a deliberately narrow question. The General Assembly asked whether Kosovo’s unilateral declaration of independence was in accordance with international law. The Court concluded that the declaration adopted on February 17, 2008 did not violate general international law, Security Council Resolution 1244 or the Constitutional Framework applicable in Kosovo (ICJ, 2010).

A finding that international law does not prohibit an act is not equivalent to finding that international law confers a right to perform it. The Court expressly declined to determine whether international law generally provides a positive entitlement to unilateral secession. It likewise did not decide whether a general doctrine of remedial secession exists.

Three legal questions consequently remain distinct. International law may contain no general prohibition on issuing a declaration of independence; the entity concerned may still lack an international legal right to secede; and domestic institutions may remain constitutionally unable to initiate or implement separation.

That distinction is directly relevant to Scotland and Wales. The absence of a general international prohibition on declarations of independence cannot expand the statutory competence of the Scottish Parliament or the Senedd. The powers of those legislatures derive from domestic devolution legislation, while the Kosovo opinion addresses a separate question concerning the requirements of international law.

3. Scottish Independence and the Referendum Power

For Scotland, the immediate legal question is not whether an independent Scottish state could ever lawfully exist. It is whether the Scottish Parliament presently has legislative authority to organize a referendum whose purpose is to ask whether Scotland should leave the United Kingdom. The Scotland Act 1998 supplies the controlling domestic framework.

Section 29(2)(b) provides that legislation of the Scottish Parliament is outside competence so far as it relates to reserved matters. Schedule 5 reserves both “the Union of the Kingdoms of Scotland and England” and “the Parliament of the United Kingdom” (Scotland Act 1998).

That allocation of competence does not make Scottish independence legally impossible. The statutory settlement can be modified, and the UK Parliament can authorize a referendum directly or enable Holyrood to legislate for one. The distinction is between the possibility of constitutional change and the authority presently available to initiate it through devolved legislation.

3.1 Why the 2014 Referendum Was Lawful

The 2014 referendum did not rest on an inherent power of the Scottish Parliament to determine the future of the Union. It followed political agreement between the UK and Scottish governments. Under the Edinburgh Agreement of October 15, 2012, both governments committed themselves to a referendum with a clear legal basis that would be legislated for by the Scottish Parliament.

Legal authority was supplied by the Scotland Act 1998 (Modification of Schedule 5) Order 2013. Made under section 30 of the Scotland Act, the Order temporarily modified Schedule 5 so that legislation for a single Scottish independence referendum meeting specified conditions would fall within Holyrood’s legislative competence.

The legal effect of the Order was specific rather than permanent. It created an exception to the reserved-matters framework for the referendum held in 2014 and did not generally remove questions concerning the Union from Schedule 5. The Scottish Parliament subsequently enacted the legislation governing the referendum within that temporary competence.

The 2014 precedent consequently demonstrates that the UK constitutional order can accommodate a lawful referendum on Scottish independence. It does not establish a continuing devolved power to hold further independence referendums without another change to the statutory framework.

3.2 What the UK Supreme Court Decided in 2022

The competence issue returned to the courts when the Lord Advocate referred a proposed Scottish Independence Referendum Bill to the UK Supreme Court. The Bill would have provided for a referendum asking whether Scotland should be an independent country. The Scottish Government argued that the proposed vote would be advisory and would not itself alter Scotland’s legal status.

In Reference by the Lord Advocate of Devolution Issues under Paragraph 34 of Schedule 6 to the Scotland Act 1998, the Court unanimously held that the proposed provision related to reserved matters and therefore fell outside the Scottish Parliament’s legislative competence ([2022] UKSC 31). Both the Union and the UK Parliament were directly engaged by legislation whose subject was Scottish independence.

The proposed referendum’s advisory character did not alter the conclusion. The Court held that a lawfully conducted referendum could have significant political consequences even without producing immediate legal change. A majority vote for independence could affect the democratic legitimacy of the Union and strengthen the political authority of the independence claim (UK Supreme Court, 2022).

The Court also rejected the argument that international self-determination required a different interpretation of the Scotland Act. Drawing on the Supreme Court of Canada’s reasoning in the Quebec Secession Reference, it concluded that the exceptional circumstances associated with external self-determination were not present in Scotland and that the Canadian court’s observations applied with equal force to the Scottish case (UK Supreme Court, 2022).

The judgment did not decide that Scotland can never become independent or that a future referendum would necessarily be unlawful. Its holding concerned the distribution of legislative competence under the Scotland Act as it then stood. Parliament remains capable of altering that distribution.

3.3 What a New Scottish Referendum Would Require

A future referendum could again be enabled through a section 30 Order modifying Schedule 5. Such an Order would require the statutory approval process prescribed by the Scotland Act. Alternatively, the UK Parliament could enact primary legislation authorizing a referendum or amend the devolution settlement so that referendum legislation no longer falls within the relevant reservation.

Recent proposals have not yet changed that position. On August 28, 2026, the Scottish Government published a draft Independence Referendum Bill proposing the same core question used in 2014. The government stated that the Bill would be introduced once the necessary legislative powers had been secured (Scottish Government, 2026).

A separate Scotland (Independence Referendum) Bill was introduced in the House of Commons on June 22, 2026. The Private Member’s Bill proposes amending Schedule 5 to the Scotland Act so that a referendum on Scottish independence would cease to be reserved. As of September 13, 2026, it had not become law, and its second reading was scheduled for November 27, 2026 (UK Parliament, 2026).

Political mandate and legislative competence remain separate. Electoral support for independence, a manifesto commitment or a parliamentary resolution may place significant political pressure on Westminster. None of those developments, without legal change, modifies Schedule 5 or independently gives Holyrood competence to legislate for an independence referendum.

4. Wales and the Limits of Devolved Constitutional Power

Wales operates under a different devolution statute and must be assessed on its own legal terms. The Wales Act 2017 amended the Government of Wales Act 2006 to introduce a reserved-powers model, which came into force on April 1, 2018. Under section 108A, the Senedd may legislate within its devolved competence subject to the reservations and restrictions set out in the Act.

The constitutional reservations are explicit. Schedule 7A reserves the Crown, “the union of the nations of Wales and England” and “the Parliament of the United Kingdom” (Government of Wales Act 2006, sch. 7A). Legislation directed at ending the Union between Wales and England would accordingly engage matters that Parliament has expressly withheld from devolved competence.

No Welsh counterpart to the 2022 Scottish independence reference has determined the legality of a hypothetical Senedd referendum bill. The Scottish judgment should not be treated as though it directly decides every issue under the differently drafted Welsh settlement. Any legal challenge would have to be resolved by applying the competence provisions of the Government of Wales Act to the purpose and effect of the particular Welsh legislation.

The statutory text nevertheless creates a substantial obstacle to a unilateral Senedd referendum on independence. A measure specifically concerned with whether Wales should cease to form part of the United Kingdom would be closely connected to the expressly reserved union of Wales and England. The precise legal assessment would depend on the legislation enacted, but the Senedd does not presently possess a general devolved competence over that constitutional question.

The settlement can be altered through lawful constitutional procedures. The UK Parliament may amend the Government of Wales Act through primary legislation, while section 109 permits Schedules 7A and 7B to be amended by Order in Council subject to the approvals required by the Act, including approval by both Houses of Parliament and the Senedd.

Welsh independence may also be pursued through ordinary democratic politics. Elections, party mandates, Senedd resolutions and negotiations can create political pressure for a referendum or wider constitutional change. They do not, without an alteration of legal competence, authorize the Senedd to determine the future of the Union unilaterally.

Wales consequently lacks the pre-existing statutory mechanism found in Northern Ireland. The Northern Ireland framework provides a legally regulated process through which a vote on constitutional status may be held and, if the statutory conditions and a majority for Irish unity are satisfied, through which further legal and intergovernmental steps toward implementation must follow. Wales has no equivalent standing procedure.

5. Northern Ireland Has a Different Legal Route

Northern Ireland cannot be placed within the same legal category as Scotland and Wales. Its constitutional status is governed not only by devolution legislation but by the settlement created through the Belfast/Good Friday Agreement and implemented in the Northern Ireland Act 1998. Those arrangements expressly contemplate a lawful change from membership of the United Kingdom to membership of a united Ireland.

Describing this simply as a general “right to secede” would be inaccurate. Northern Ireland has no standing legal entitlement to establish itself as an independent sovereign state. The constitutional choice recognized by the 1998 settlement is between remaining within the United Kingdom and becoming part of a united Ireland, with that choice governed by the principle of consent (Belfast Agreement, 1998; Northern Ireland Act 1998, s. 1).

The resulting mechanism is specific to Northern Ireland. It emerged from a negotiated peace settlement involving the United Kingdom, Ireland and political parties in Northern Ireland and was subsequently incorporated into both international and domestic legal arrangements. Its existence does not establish an equivalent referendum entitlement for Scotland or Wales.

5.1 The Good Friday Agreement and the Principle of Consent

The expression “Good Friday Agreement” encompasses two interconnected instruments with different legal characteristics. The Multi-Party Agreement was concluded among the British and Irish governments and most of the political parties participating in the negotiations. Alongside it stands the British-Irish Agreement, an international agreement between the United Kingdom and Ireland through which the two governments assumed commitments concerning the constitutional settlement and implementation of the wider agreement (Belfast Agreement, 1998; British-Irish Agreement, 1998).

The principle of consent is central to the settlement. The two governments recognized the legitimacy of whatever choice is freely exercised by a majority of the people of Northern Ireland concerning whether they prefer to continue supporting the Union with Great Britain or form part of a sovereign united Ireland. They also recognized the right of the people of the island of Ireland to exercise self-determination by agreement between its two parts and on the basis of consent (British-Irish Agreement, 1998, art. 1).

Consent operates in both directions. Northern Ireland cannot be removed from the United Kingdom contrary to the wishes of a majority of its population, but continued membership of the Union is not constitutionally fixed regardless of future democratic choice. The settlement expressly accepts that Northern Ireland’s constitutional status may change if the required majorities support that outcome.

The Irish constitutional order was amended accordingly. Article 3.1 of the Constitution of Ireland provides that a united Ireland may be brought about only by peaceful means with the consent of a majority democratically expressed in both jurisdictions on the island. The constitutional settlement thus replaced the previous territorial claim with an agreed process based on democratic consent (Constitution of Ireland, art. 3).

The international agreement also contains an implementation commitment. If the right of self-determination is exercised under the agreed conditions in favor of Irish unity, the British and Irish governments are under a binding obligation to introduce and support legislation in their respective parliaments to give effect to that choice (British-Irish Agreement, 1998, art. 1(iv)).

Nothing in this framework establishes a general rule requiring the United Kingdom to provide equivalent mechanisms elsewhere. Northern Ireland’s arrangements reflect the particular history of the conflict, the interstate relationship between the United Kingdom and Ireland, and the compromises embodied in the 1998 peace settlement. Scotland and Wales cannot acquire the same statutory machinery merely by invoking the broader political principle of democratic choice.

5.2 The Border Poll Under the Northern Ireland Act

The Northern Ireland Act 1998 gives domestic legal effect to the consent principle. Section 1 provides that Northern Ireland remains part of the United Kingdom and shall not cease to be so without the consent of a majority voting in a poll held under Schedule 1. If a majority votes for Northern Ireland to cease being part of the United Kingdom and form part of a united Ireland, the Secretary of State must lay before Parliament proposals designed to give effect to that wish (Northern Ireland Act 1998, s. 1).

Schedule 1 distinguishes discretion from legal duty. Paragraph 1 permits the Secretary of State to direct the holding of a poll. Paragraph 2 requires the Secretary of State to do so if it appears likely that a majority of those voting would express a wish for Northern Ireland to cease being part of the United Kingdom and form part of a united Ireland, subject to the statutory restriction on repeat polls (Northern Ireland Act 1998, sch. 1).

The statute does not prescribe a particular opinion-poll percentage, election result or demographic threshold for determining when that likelihood test is met. In McCord, Re Application for Judicial Review [2020] NICA 23, the Northern Ireland Court of Appeal confirmed that the assessment may depend on a range of relevant evidence and that the Secretary of State must approach the statutory responsibilities honestly and with rigorous impartiality.

The Secretary of State cannot, however, bring a border-poll order into force entirely alone. Under section 96(2) of the Northern Ireland Act, an order under Schedule 1 must be made by statutory instrument and cannot be made unless a draft has been approved by both Houses of Parliament. Parliament thus participates in the statutory process before the poll as well as in any later implementation.

Successive polls are also subject to a minimum interval. Paragraph 3 of Schedule 1 prevents another poll from being held within seven years of an earlier Schedule 1 poll. Because the mandatory duty in paragraph 2 is expressly subject to paragraph 3, the likelihood condition cannot require another referendum during that seven-year period.

A majority for Irish unity would not transfer sovereignty immediately upon announcement of the result. Section 1(2) requires the Secretary of State to place implementation proposals before Parliament, while the British-Irish Agreement requires action by both governments. The Irish constitutional framework separately requires democratically expressed consent in both jurisdictions.

The precise institutional design of any eventual united Ireland is not exhaustively predetermined by the 1998 settlement. Questions concerning governmental structures, constitutional arrangements and the practical terms of unity would require further agreement and legislation. The law establishes a route to constitutional change and binding duties within that route; it does not supply every detail of the constitutional order that would follow.

6. Three Different Meanings of a “Right to Decide”

A “right to decide” can refer to several legally distinct propositions. It may express a political claim that democratic legitimacy requires a population to determine its constitutional future. It may invoke the international-law right of self-determination. Or it may refer to domestic constitutional authority to call a referendum and implement its result. These ideas can overlap politically, but they do not create a single legal entitlement.

Scotland illustrates the difference clearly. The Scotland Act 1998 and the UK Supreme Court’s 2022 judgment establish that Holyrood does not currently possess unilateral competence to legislate for an independence referendum. A lawful route nevertheless exists: Westminster may authorize a referendum directly or modify devolved competence, as occurred before the 2014 vote. A successful referendum would carry substantial democratic authority, but it would still require further legal implementation before Scotland became an independent state.

Wales occupies a comparable but distinct position. The Government of Wales Act 2006, as amended, reserves the Union and the UK Parliament, and there is no standing statutory mechanism allowing the Senedd to call an independence referendum on its own authority. Welsh independence could be pursued politically and could ultimately be authorized through constitutional change, but a referendum result would not automatically create an independent Welsh state without subsequent legislation and agreement.

Northern Ireland is materially different. The Belfast/Good Friday Agreement and the Northern Ireland Act 1998 already contain a consent-based mechanism governing constitutional status. Schedule 1 permits a border poll and places the Secretary of State under a duty to initiate the process when the statutory likelihood threshold is satisfied, subject to the seven-year restriction and parliamentary approval of the poll order. A majority for Irish unity would then activate statutory and treaty-based duties toward implementation rather than producing an immediate constitutional transfer.

The role of international law also differs across the three cases. General principles of self-determination are relevant to Scotland, Wales and Northern Ireland, but only Northern Ireland’s constitutional position is additionally structured by a bilateral international agreement between the United Kingdom and Ireland. Describing all three situations through the same phrase, such as a “right to decide,” risks obscuring differences in legal source, referendum authority, institutional procedure and the consequences of a successful vote.

The central point is that political entitlement, international self-determination and domestic referendum competence must remain separate. Scotland has a demonstrated route to an agreed referendum but no present unilateral devolved power to legislate for one. Wales likewise lacks unilateral authority over its constitutional status. Northern Ireland alone possesses an existing statutory and treaty-based mechanism under which specified legal conditions can trigger a formal process for changing its place within the United Kingdom.

7. Can Westminster Refuse an Independence Referendum?

Under the law currently in force, an electoral mandate for another Scottish independence referendum does not itself place the UK Government or Parliament under a statutory duty to authorize one. The Scotland Act contains no mechanism by which a manifesto commitment, Scottish parliamentary majority or specified level of public support automatically triggers a referendum.

The 2014 vote occurred because the UK and Scottish governments reached an agreement and the legal competence of the Scottish Parliament was temporarily modified. A section 30 Order remains one possible route, and the UK Parliament could legislate directly. Neither process is automatically activated by an election result.

A majority of the Scottish Parliament’s Constitution, Europe, External Affairs and Culture Committee concluded in its 2026 inquiry that no existing statutory process enables a Scottish independence referendum to be compelled without the agreement of the UK Parliament (Scottish Parliament, 2026). The Committee was divided on its principal conclusions, so the report does not represent an uncontested cross-party constitutional position.

Political consequences may nonetheless be significant. The UK Supreme Court recognized in 2022 that a referendum could affect the democratic legitimacy of the Union and the political authority of the independence movement even if the result had no immediate legal effect (UK Supreme Court, 2022). Sustained electoral support may create constitutional pressure for negotiation without producing an enforceable legal obligation to authorize a referendum.

Wales stands in a comparable position on this issue. Neither the Government of Wales Act 2006 nor existing international law requires the UK Government to authorize a Welsh independence referendum once public support reaches a particular level. Political arguments based on democratic legitimacy remain separate from the statutory competence necessary to hold such a referendum.

International self-determination does not presently create a general duty requiring the United Kingdom to hold secession referendums in Scotland or Wales. In relation to Scotland, the Supreme Court rejected the argument that the right of self-determination altered the statutory distribution of legislative competence. More generally, no established rule of international law requires a democratic state to organize a secession referendum whenever a territorially concentrated majority demands one.

Northern Ireland is different because Schedule 1 contains a statutory trigger. Once it appears likely to the Secretary of State that a majority voting would favor Irish unity, paragraph 2 imposes a duty to initiate the poll process, subject to the seven-year restriction and the requirement that the resulting order receive parliamentary approval. The Secretary of State cannot lawfully treat the statutory condition as politically optional.

The UK Parliament could, as a matter of domestic constitutional law, enact primary legislation altering the Northern Ireland Act. That does not mean that domestic legislation could erase the United Kingdom’s international obligations. The British-Irish Agreement remains binding at the international level, and the Vienna Convention principle that a state may not invoke its internal law as justification for failure to perform a treaty applies independently of questions concerning the domestic validity of an Act of Parliament (Vienna Convention on the Law of Treaties, 1969, art. 27).

8. A Yes Vote Would Not Automatically Create a New State

A referendum result and the legal creation of a new state are different events. The UK Supreme Court emphasized that the proposed Scottish independence referendum would not itself change the law or terminate the Union. Even a lawful majority for independence would first provide democratic authorization for further constitutional action rather than immediately creating a sovereign Scottish state (UK Supreme Court, 2022).

Implementation would require legislation and negotiations establishing the terms and effective date of separation. Questions concerning public assets and liabilities, citizenship, governmental institutions, borders and public debt would have to be resolved as part of that process. The distribution of existing rights and obligations could not be inferred simply from the referendum result.

International questions would arise alongside the domestic settlement. Treaty relations, participation in international organizations, diplomatic representation and the respective legal positions of an independent Scotland and the continuing United Kingdom would require separate consideration. International law provides principles and practice relevant to those issues, but the precise consequences would depend heavily on the terms of separation.

A hypothetical Welsh referendum would involve the same basic separation between democratic choice and legal implementation. Wales has no current mechanism under which a majority vote itself terminates its constitutional relationship with the United Kingdom. An authorized vote for independence would still require legislation and agreement giving legal effect to the decision.

Northern Ireland follows a different route because the constitutional alternative is Irish unity, not independent Northern Irish statehood. Yet its referendum is not self-executing either. A majority for unity would activate statutory and treaty-based implementation obligations, while legislation and democratic consent in both jurisdictions would remain part of the agreed process (Northern Ireland Act 1998, s. 1; British-Irish Agreement, 1998; Constitution of Ireland, art. 3).

The legal consequences of any referendum must consequently be derived from the instrument authorizing it. None of the existing arrangements applicable to Scotland, Wales or Northern Ireland supports the proposition that an affirmative vote, standing alone, would instantaneously establish the final constitutional status sought by the majority.

9. Recognition and Statehood Do Not Create a Shortcut

Recognition becomes relevant once an entity claims the status of a state; it does not confer domestic constitutional authority to create one. Recognition of an independent Scotland or Wales by foreign governments could have substantial international consequences after separation, but it could not beforehand amend the Scotland Act or the Government of Wales Act or enlarge the competence of either devolved legislature.

The Montevideo Convention on the Rights and Duties of States identifies a permanent population, defined territory, government and capacity to enter into relations with other states as qualifications associated with statehood. Article 3 adopts the declaratory proposition that the political existence of a state is independent of recognition by other states (Montevideo Convention, 1933). The United Kingdom is not a party to the Convention, and the instrument is an inter-American treaty rather than a universal code, although its formulation remains highly influential in discussions of statehood.

Recognition nonetheless has considerable practical and political significance. International law has long debated declaratory and constitutive theories of recognition, and state practice does not reduce recognition to a mechanical application of formal criteria. Broad diplomatic acceptance can strengthen the international position of a new state, while widespread non-recognition can severely constrain its participation in international relations (Klabbers, 2024).

That practical importance does not alter the order of the legal questions. Recognition cannot retrospectively supply Holyrood or the Senedd with powers withheld by their respective devolution statutes. Domestic authority to initiate constitutional separation and the international response to the resulting entity belong to different stages of the process.

State succession raises a further set of questions if separation actually occurs. Treaty relations, state property, debts, archives, nationality and membership of international organizations may all require resolution. The 1978 Vienna Convention on Succession of States in Respect of Treaties provides one framework for treaty succession, but its limited participation and the diversity of state practice mean that succession questions frequently depend on agreement and context rather than a single comprehensive rule (Klabbers, 2024).

The existence of those international rules does not generate an antecedent right of secession. A claim to independence concerns authority to change constitutional status; statehood concerns the international legal existence of the resulting entity; recognition concerns the response of other states; and succession concerns the allocation or continuation of legal relationships after the change. Conflating those stages would make international recognition appear to solve a constitutional question that arises much earlier.

Conclusion

Scotland, Wales and Northern Ireland can all undergo lawful constitutional change, but they do not presently possess the same legal route to leaving the United Kingdom. Scotland can hold another lawful independence referendum if the necessary authority is conferred, yet the Scottish Parliament cannot currently legislate for one unilaterally. Wales likewise lacks devolved competence over the Union and has no standing statutory mechanism for an independence referendum.

Northern Ireland occupies a distinct position in both domestic and international law. The Belfast/Good Friday Agreement and the Northern Ireland Act 1998 provide an existing consent-based framework through which its constitutional status may change from membership of the United Kingdom to membership of a united Ireland. The statutory process involves the Secretary of State, parliamentary approval of the poll order and, following a vote for unity, further legislative and intergovernmental implementation.

International self-determination does not collapse these different constitutional arrangements into a single right of secession. It does not presently confer on Scotland or Wales a general unilateral entitlement to leave the United Kingdom, and the Kosovo advisory opinion does not establish such a right. Democratic support for independence can carry substantial political authority without itself creating legislative competence or an enforceable international entitlement to separation.

The planned Cardiff memorandum can strengthen a common political argument that constitutional status should remain open to democratic choice. It cannot create powers withheld by the respective devolution settlements or reproduce Northern Ireland’s treaty-based mechanism elsewhere in the United Kingdom. A claim to self-determination, the domestic authority to hold a referendum and a legal entitlement to alter sovereignty remain separate questions—and Scotland, Wales and Northern Ireland do not receive the same answer to each of them.

References

Agreement between the United Kingdom Government and the Scottish Government on a Referendum on Independence for Scotland (2012) Edinburgh, 15 October 2012 [online]. Available at: https://assets.publishing.service.gov.uk/media/5a7eae5740f0b62305b827ce/scottish_referendum_agreement.pdf (Accessed: 13 September 2026).

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