The Justice Department is highly likely to appeal the decision, and the issue may eventually reach the Supreme Court. By dismissing the entire indictment, Cannon’s decision also means that the charges are dropped for Trump’s two co-defendants, Waltine “Walt” Nauta and Carlos De Oliveira.

Even if Cannon’s ruling is eventually overruled, the decision to dismiss Trump’s indictment adds to a string of legal victories for him in recent weeks, including a sweeping Supreme Court ruling July 1 that gives former presidents broad immunity for their official acts while in office.

At the Justice Department, Attorney General Merrick Garland declined to comment on the ruling. A spokesman for Smith did not immediately comment.

On social media, Trump said Monday’s dismissal “should be just the first step” and that the rest of the criminal and civil cases against him also should be tossed out of court. He accused Democrats of conspiring against him to bring those cases, a claim that has been repeatedly denied by federal, state, and local officials.

“Let us come together to END all Weaponization of our Justice System,” he wrote.

Trump’s significant legal victory comes less than 48 hours after he survived an assassination attempt in Butler, Pa., and as Trump was preparing to be formally nominated as the Republican presidential candidate at the Republican National Convention in Milwaukee.

After Cannon’s decision, one person who had been told they could be called as a witness in the documents case described Trump as “the luckiest man on earth.” The person spoke on the condition of anonymity to describe candid feelings about the development.

Trump attorneys have long considered the classified documents case to be the strongest of the four criminal cases against him — in part because the acts in question mostly occurred after he left the White House — and it was the case that most worried them. The documents case has been particularly concerning to Trump advisers because if it ever does go to trial, it would feature first-person accounts from people in his inner orbit describing conversations with him.

The former president was charged with 40 counts of illegally retaining classified defense information and obstructing government efforts to retrieve the material. Some of the documents found in an FBI search of Mar-a-Lago, his Florida home and private club, contained information about top-secret U.S. operations so closely guarded that many senior national security officials are kept in the dark about them, The Washington Post reported last year.

Cannon’s opinion delves into the legal minutiae of special counsel regulations and does not address the crimes Trump and his co-defendants are accused of committing, or the merits of the evidence that prosecutors have collected.

The former president was convicted in May of falsifying records to conceal a hush money payment to an adult-film actress ahead of the 2016 election, but he is now challenging that verdict and the indictment itself based on the Supreme Court’s immunity ruling. Two other cases — his federal election-interference case in D.C. and a similar state trial in Georgia — have been stalled by legal challenges and will also be impacted by the immunity decision.

Cannon, who was nominated to the federal bench by Trump, wrote that the issue of a special counsel was a novel one that had to be decided before the prosecution could proceed any further.

“Upon careful study of the foundational challenges raised in the Motion, the Court is convinced that … Smith’s prosecution of this action breaches two structural cornerstones of our constitutional scheme — the role of Congress in the appointment of constitutional officers, and the role of Congress in authorizing expenditures by law,” Cannon concluded in her order.

Cannon found that the Justice Department has inconsistently appointed special counsels and said the “lack of consistency makes it near impossible to draw any meaningful conclusions about Congress’s approval of modern special counsels like Special Counsel Smith.”

She said Smith’s degree of autonomy made him a different type of prosecutor.

“In fact, very few historic special attorneys resemble Special Counsel Smith. For starters, the title ‘special counsel’ is of fairly recent vintage. Special-attorney-like figures bore many titles throughout the decades,” Cannon wrote. “In the Court’s view, this is not an insignificant semantic detail.”

Cannon has long been skeptical of prosecutors’ decision-making in the documents case, but Monday’s decision is her most consequential expression of that skepticism by far. In 2022, after FBI agents searched Trump’s home and found more than 100 classified documents, Cannon appointed a special master — essentially an extra judge — to scrutinize what documents investigators seized. An appeals court later reversed her special master appointment.

“She has been open to and often embraced some of the more aggressive — even outlandish — arguments of Trump’s lawyers and appears to have done so here,” said Daniel Richman, a professor at Columbia Law School.

The legal theory that Smith was illegally appointed and funded has generally been considered far-fetched, particularly given the recent history of special counsel appointments, including that of former FBI Director Robert S. Mueller III in 2017 to investigate any possible ties between the Trump presidential campaign and Russian election interference efforts. The Mueller appointment was also challenged in court, but two district court judges and an appeals court panel upheld it as legitimate.

Trump’s lawyers did not adopt the argument attacking the very premise of the special counsel appointment until conservative legal groups pushed it. Nor did the former president’s lawyers make a similar request to dismiss Trump’s federal election interference case in D.C. — even though Garland appointed Smith to oversee that case in the same way as the Florida case.

But the legal argument gained more steam this month after Supreme Court Justice Clarence Thomas wrote in the presidential immunity case that the special counsel’s office needs to be established by Congress and that Smith needed to be confirmed by the Senate. Thomas urged lower courts to explore the issue. The justice wrote that he tacked on his concurring opinion to the immunity ruling to “highlight another way in which this prosecution may violate our constitutional structure.”

In Monday’s ruling, Cannon cited Thomas’s opinion — which none of the other justices signed on to — multiple times.

She agreed with Trump’s attorney that she is not bound by every aspect of the unanimous 1974 Supreme Court opinion in U.S.A. vs Nixon, which forced President Richard Nixon to hand over to a federal court tape recordings and other subpoenaed materials related to the Watergate scandal.

As part of that opinion, the justices wrote that Congress has given the attorney general the authority to appoint a special prosecutor — an earlier iteration of a special counsel — to handle key duties of the department. That assertion was not a central part of the 50-year-old ruling, Cannon concluded, explaining why she did not believe the language dictated the constitutionality of special counsels.

“Cannon has brushed aside language from U.S.A vs Nixon and embraced the opinion of the single justice,” Richman said.

Cannon held two hearings on the appointment of the special counsel last month, a few weeks before Thomas issued his opinion. During the hearing, it was not clear how she would rule, but she acknowledged that precedent seemed to support Garland’s appointment of Smith and that there would be a high legal bar for overturning it.

The crux of Trump’s argument is that because Garland has repeatedly said Smith is acting independently in overseeing the investigation, the special counsel should be considered a “principal officer” — a top government official who has no immediate supervisor and whose appointment requires Senate approval.

The special counsel team countered that Smith, like other special counsels before him, is not a principal officer. The team said that while federal regulations say Garland does not provide day-to-day supervision of special counsels, the attorney general ensures that they adhere to Justice Department protocols and can review major investigatory steps.

In an unusual move, Cannon invited outside groups to participate in the hearings and offer their arguments for and against the appointment of Smith.

“What do you make of this potentially tolerated practice?” Cannon asked outside attorney Gene Schaerr, noting that previous attorneys general have made appointments similar to Garland’s naming of Smith.

Josh Dawsey in Milwaukee contributed to this report.