DENVER — In an unprecedented ruling citing an obscure section of the 14th Amendment related to insurrection, the Colorado Supreme Court has disqualified former President Donald J. Trump from appearing on the state’s 2024 presidential primary ballot.
The 4-3 decision on Tuesday represents the first time a court has invoked Section 3 of the Amendment to bar a current or former federal officeholder from running again. Enacted after the Civil War, Section 3 prohibits those who have taken an oath to protect the Constitution but engaged in “insurrection or rebellion” against the United States from holding state or federal office.
While the ruling applies only to Colorado’s presidential primary next March, it could carry implications for Mr. Trump’s ability to secure the Republican nomination if other battleground states where he is competitive were to take similar action. For now, Mr. Trump’s allies have vowed to appeal, setting up a race to get the issue before the U.S. Supreme Court.
In its 49-page opinion, the majority wrote that they did not come to the decision easily given the significance of disallowing a former president’s name from the ballot. But they ultimately concluded that Mr. Trump’s efforts to overturn his 2020 electoral defeat met the definition of engaging in an insurrection under Section 3.
“President Trump’s actions, detailed at length…unquestionably constitute ‘engaging’ in ‘insurrection,” the opinion read, citing his baseless claims of election fraud, his public exhortations to supporters before the riot and his tepid response as the violence engulfed the Capitol. Two state courts have also held that Mr. Trump incited the attack that interrupted the certification of the 2020 election results.
The ruling, which is on hold pending appeal, does not directly affect Mr. Trump’s ability to run in most other states. But Democratic groups supporting the effort argue that it could provide momentum for additional legal bids to have election officials declare him ineligible under the 14th Amendment elsewhere.
For Mr. Trump, 76, the decision represents the latest legal threat to an expected 2024 campaign that his allies had hoped to fast track to box out potential Republican rivals. Federal and state prosecutors are pursuing investigations related to Mr. Trump’s attempts to cling to power in 2020 and his handling of classified documents after leaving office. And on Tuesday, the House Jan. 6 committee voted unanimously to refer Mr. Trump to the Justice Department for criminal prosecution linked to both efforts.
Even if Mr. Trump were to ultimately prevail legally, Democrats view the cases as effectively serving to remind voters of what they view as Mr. Trump’s disqualifying offenses. “It hurts from an electoral perspective,” said one Democrat working on the 2024 presidential race, “raising yet again what he did.”
The Colorado decision turns on both procedural and substantive questions that are likely to confront the more conservative U.S. Supreme Court if Mr. Trump’s legal team moves to get it reversed. His lawyers argue that Section 3 does not apply to the presidency at all. And they say that holding Mr. Trump responsible for the Jan. 6 attack without giving him a chance to mount a defense in a Senate impeachment trial violates constitutional due process protections.
Justice Carlos A. Samour Jr., joined by two other dissenters, agreed on that latter procedural point. He called Mr. Trump’s efforts to reverse his electoral loss “repugnant.” But Justice Samour said that relying on a state proceeding, rather than congressional impeachment, to invoke Section 3’s bar on holding future office contravened Constitutional safeguards.
“Preventing people from seeking public office is no trivial matter,” he wrote. “It deserves the full process due before someone’s right to run for office is stripped away, particularly when that individual was previously elected to the same office as that being denied.”
Free Speech For People, an advocacy group, filed the Colorado lawsuit days after the Jan. 6 attack on plaintiffs’ behalf, including Eric O’Neill, a former F.B.I. counterterrorism investigator who infiltrated organized crime.
Noah Bookbinder, president of Citizens for Responsibility and Ethics in Washington, which brought the case with Free Speech for People, said the ruling “shows that the Constitution applying equally means applying to all — even a former U.S. president.”
Top Republicans denounced the decision as legally dubious while predicting that it could galvanize Mr. Trump’s supporters.
“Regardless of political affiliation, every citizen registered to vote should not be denied the right to support our former president and the individual who is the leader in every poll of the Republican primary,” said Representative Mike Johnson of Louisiana, the chairman of the conservative House Freedom Caucus.
Mr. Trump’s campaign promised a swift appeal even as it used the Colorado decision in a new fund-raising pitch portraying the ruling as more evidence that elites are aligned against ordinary Americans.
“The Radical Left is so afraid of Trump they are willing to rewrite history, defy the Constitution, and even destroy Democracy to stop HIM,” read a campaign text message appeal on Tuesday evening. “This is how dictatorships are born.”
In the view of Mr. Trump’s team, time remains on its side for now, given the calendar. They note that even once litigation concludes, the Colorado opinion does not go into effect until Jan. 4, 2024, days before a mid-January deadline for the state to certify its primary ballot. And they believe that conservative justices on the Supreme Court will view the novel effort skeptically.
On Tuesday, as word of his potential barring spread, Mr. Trump made no mention of the Colorado ruling during a speech at a fund-raiser, focusing instead on sharp criticism of Mr. Biden, China and Iran.
Behind the scenes, though, his political operation had begun discussing contingencies for navigating multiple primaries with him left off ballots should their legal efforts falter. Under most state laws, Mr. Trump’s loyal slate of delegates could vote for him at contested national conventions even if he did not compete directly in state primaries. But it would prompt an ugly floor fight at a divided convention.
Conservatives on the Supreme Court have already proven sympathetic to arguments that state elections procedures favored by Democrats have gone too far. Last year, the court limited the power of state courts to review congressional redistricting maps, a ruling viewed as helpful to Republican efforts to retake the House this fall.
Some election lawyers unaffiliated with Mr. Trump say the dissenting opinion in the Colorado case highlights genuine concerns with the procedural path taken to apply Section 3 against a former president.
“There’s a fairness issue,” said Derek T. Muller, an election law professor at the University of Iowa College of Law. “If you’re going to exclude someone from something as important as running from public office, you would want better procedures.”
Still, Professor Muller said most legal scholars had viewed Section 3 as a virtually dead letter given how infrequently it had ever been employed. The law barring Mr. Trump in Colorado, he said, represents “a novel and aggressive interpretation.”
Democrats, bracing for a fiercely contested presidential primary fight of their own in 2024, have privately discussed ways of exacerbating Republican divisions stoked by the legal attacks on Mr. Trump. And some voiced quiet satisfaction at the ruling in Colorado.
“It’s important from a moral perspective,” said Don Fowler, a former Democratic National Committee chairman, “to once again show Trump’s illegal and unconstitutional acts.”
