WASHINGTON — The federal judge presiding over the classified documents case of former President Donald Trump in Florida dismissed the prosecution on Monday, siding with defense lawyers who said the special counsel who filed the charges was illegally appointed.

The decision by U.S. District Judge Aileen Cannon brings a stunning and abrupt conclusion to a criminal case that at the time it was filed was widely regarded as the most perilous of all the legal threats that the Republican former president confronted. Trump faced dozens of felony counts accusing him of illegally hoarding classified documents at his Mar-a-Lago estate in Palm Beach, Florida, and obstructing FBI efforts to get them back.

Defense lawyers filed multiple challenges to the case, including a legally technical one that asserted that special counsel Jack Smith had been illegally appointed under the Constitution's Appointments Clause, which governs the appointment of certain government positions, and that his office was improperly funded by the Justice Department.

Cannon, whose handling of the case had drawn scrutiny since before the charges were even filed, agreed, writing in a 93-page order: "The Framers gave Congress a pivotal role in the appointment of principal and inferior officers. That role cannot be usurped by the Executive Branch or diffused elsewhere — whether in this case or in another case, whether in times of heightened national need or not."

Smith's team had vigorously contested the argument during hearings before Cannon last month and told Cannon that even if ruled in the defense team's favor, the proper correction would not be to dismiss the entire case.

A spokesman for the Smith team did not immediately return a request seeking comment, and the Trump team did not immediately have a comment.