Last spring, Will Scharf, an arch-conservative lawyer serving as the White House staff secretary, wrote a secret memo to the chief of staff that reflected growing unease in the West Wing about one of the extreme measures being weighed by Stephen Miller, the powerful adviser driving President Trump’s deportation campaign.

Dated April 29, 2025, and stamped “confidential,” the memo was careful and lawyerly but amounted to a warning against end-running the rule of law. The subject line read: “THE WRIT OF HABEAS CORPUS.”

Habeas corpus — the centuries-old right to force the government to justify, before a judge, why it has locked a person up — is enshrined in Article I of the Constitution. Mr. Scharf’s memo, in its unassuming way, was a blinking red warning light. The second Trump White House was deliberating an explosive new claim of presidential power: the suspension of habeas rights for unauthorized immigrants.

The suspension of habeas corpus has occurred just a handful of times in U.S. history, and always under the most dire circumstances of war or invasion. Yet to a greater degree than previously known, administration officials, encouraged by Mr. Trump, actively weighed taking that step in the early months of his second term — this time to accelerate the mass deportation of immigrants in the country illegally.

Flush with a decisive 2024 election victory, Mr. Trump and some members of his team wanted to test how far the emboldened president’s authority could be pushed, setting off previously unreported internal struggles over where the limits should be.

The man who outlined his concerns in the memo, Mr. Scharf, was no resistance figure. A trim, balding, Harvard-trained lawyer who had run for office in Missouri, he had bemoaned John McCain as too moderate for the 2008 Republican nomination, and believed Mr. Trump had been vindictively prosecuted after his 2020 election loss.

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