Ricardo Gama, from the law firm Leigh Day is representing the group, and said his clients “felt they had no choice but to file court proceedings”.
“They look forward to putting their arguments to a judge,” he added.
The campaign group has now launched judicial review proceedings in the High Court, having previously launched a fundraiser to cover the legal costs of the appeal.
Cherwell District Council added in a statement that it was “confident in its decision and in the event of any judicial review will robustly defend its position”.
Meanwhile, a spokesperson for Oxford United said: “A rigorous and detailed planning process was followed by Cherwell District Council, and we look forward to supporting them defend their decision.”
Referencing the threat of a judicial review earlier this year, the club’s chairman Grant Ferguson said there were “different avenues” the club could take to fight the potential legal challenge.
He said: “We will make that decision when we really understand what the merits of the case are, or lack thereof, and how a court is likely to respond to it.”
“We are pretty comfortable that we are ahead of the curve,” he added.