WASHINGTON — A federal judge in Florida dismissed the classified documents case against former President Donald Trump on Monday, siding with defense lawyers who said the special counsel who filed the charges was illegally appointed by the Justice Department.

Hours later, special counsel Jack Smith’s office said it would appeal the order, which could result in it eventually being overturned by a higher court. But for now at least, the dismissal by U.S. District Judge Aileen Cannon brings a stunning and abrupt halt to a criminal case that at the time it was filed was widely regarded as the most perilous of all the legal threats the Republican former president confronted.

Though the case had long been stalled, and the prospect of a trial before the November election already nonexistent, the judge’s order is a significant legal and political victory for Trump as he recovers from a weekend assassination attempt and prepares to accept the Republican nomination in Milwaukee this week.

It’s the latest stroke of good fortune in the four criminal cases Trump has faced. He was convicted in May in his New York hush money trial, but the sentencing has been postponed after a Supreme Court opinion that conferred broad immunity on former presidents. That opinion will cause major delays in a separate case charging Trump with plotting to overturn his 2020 election loss to Democrat Joe Biden. Another election subversion case filed in Atlanta has been delayed by revelations of a romantic relationship between the district attorney and a special prosecutor she hired for the case.

In a statement on his social media platform, Trump said the dismissal “should be just the first step” and the three other cases, which he called “Witch Hunts,” should also be thrown out.

The classified documents case had been seen as the most legally clear-cut of the four given the breadth of evidence that prosecutors say they had accumulated, including the testimony of close aides and former lawyers, and because the conduct at issue occurred after Trump left the White House in 2021 and lost the powers of the presidency.

The indictment included dozens of felony counts accusing him of illegally hoarding classified records from his presidency at his Mar-a-Lago estate in Palm Beach, Florida, and obstructing FBI efforts to get them back. He had pleaded not guilty and denied wrongdoing.

Defense lawyers filed multiple challenges to the case, including legally technical ones that asserted that special counsel Jack Smith’s appointment by Attorney General Merrick Garland violated the Constitution’s Appointments Clause because it did not go through Congress and that Smith’s office was improperly funded by the Justice Department. She said Garland had exceeded his bounds by appointing a prosecutor without Senate approval and confirmation and had undermined the authority of Congress.

“The Special Counsel’s position effectively usurps that important legislative authority, transferring it to a Head of Department, and in the process threatening the structural liberty inherent in the separation of powers,” Cannon wrote in a 93-page order that granted the defense team’s request to dismiss the case but did not dissect the substance of the allegations against Trump.

“If the political branches wish to grant the Attorney General power to appoint Special Counsel Smith to investigate and prosecute this action with the full powers of a United States Attorney, there is a valid means by which to do so,” she added.

That mechanism is through congressional approval, she said.

A spokesman for Smith, Peter Carr, said the Justice Department had authorized an appeal.

“The dismissal of the case deviates from the uniform conclusion of all previous courts to have considered the issue that the Attorney General is statutorily authorized to appoint a special counsel,” Carr said in a statement.

The order is the latest example of the Trump-appointed judge handling the case in ways that have benefited the ex-president.

She generated intense scrutiny during the FBI’s investigation when she appointed an independent arbiter to inspect the classified documents recovered during the August 2022 search of Mar-a-Lago, a decision that was overturned months later by a unanimous federal appeals panel.

Since the charges were filed, she has been slow to issue rulings — favoring Trump’s strategy of securing delays in all his criminal cases — and has entertained defense motions and arguments that experts said other judges would have dispensed with without hearings. In May, she indefinitely canceled the trial date amid a series of unresolved legal issues.