DENVER — A Colorado judge finds that President Trump engaged in insurrection during the January 6, 2021, attack on the U.S. Capitol, yet is rejecting an effort to keep him off the state’s primary ballot because it’s unclear whether a Civil War-era Constitutional amendment barring insurrectionists from public office applies to the presidency.

The lawsuit, brought by a left-leaning group on behalf of a group of Republican and independent Colorado voters, contended that Trump’s actions related to the attack ran afoul of a clause in the 14th Amendment that prevents anyone from holding office who “engaged in insurrection or rebellion” against the Constitution.

The decision by a state district judge, Sarah Wallace, is the third ruling in a little over a week against lawsuits seeking to knock Mr. Trump off the ballot by citing Section 3 of the 14th Amendment.

The Minnesota Supreme Court last week said Mr. Trump could remain on the primary ballot because political parties have sole choice over who appears, while a Michigan judge ruled that Congress is the proper forum for deciding whether Section 3 applies to Mr. Trump.

In her decision, Judge Wallace said she found that Mr. Trump did “engage in insurrection” on January 6 and rejected his attorneys’ arguments that he was simply engaging in free speech. Normally, that would be enough to disqualify him under Section 3, but she said she couldn’t do so for a presidential candidate.Judge Sarah B. Wallace presiding over a lawsuit to keep President Trump off the ballot in Colorado, November 15, 2023, at Denver.

Section 3 does not specifically refer to the presidency, as it does members of the Senate or House of Representatives. Instead, the clause refers to “elector of President and Vice President,” along with civil and military offices.

“Part of the Court’s decision is its reluctance to embrace an interpretation which would disqualify a presidential candidate without a clear, unmistakable indication that such is the intent of Section Three,” the judge wrote in the 102-page ruling.

A Trump campaign spokesman, Steven Cheung, called the ruling “another nail in the coffin of the un-American ballot challenges.”

“These cases represent the most cynical and blatant political attempts to interfere with the upcoming presidential election by desperate Democrats,” Mr. Cheung said in a statement.

Citizens for Responsibility and Ethics in Washington, the group that filed the case, said they would appeal to the Colorado Supreme Court.

“The Court found that Donald Trump engaged in insurrection after a careful and thorough review of the evidence,” said attorney Mario Nicolais, who was representing the voters who brought the lawsuit. 

“We are very pleased with the opinion and look forward to addressing the sole legal issue on appeal,” Mr. Nicolais added, “namely whether Section 3 of the 14th Amendment applies to insurrectionist presidents.”

Whether it’s the Colorado case or one filed in another state, the question ultimately is likely to reach the Supreme Court, which has never ruled on Section 3. The group suing in the Michigan case, Free Speech for People, filed an appeal Thursday in state court.

Legal experts said it was significant that Judge Wallace found Mr. Trump had engaged in insurrection. She wrote that she agreed with the petitioners’ claim that he “incited” the attack.

“It’s a stunning holding for a court to conclude that a former president engaged in insurrection against the United States,” said a Notre Dame law professor, Derek Muller, who has followed the case closely. “And there’s a good chance that, on appeal, a court bars him from the ballot.”

Mr. Trump has called the attempt to remove “election interference” funded by “dark money” Democratic groups. His attorneys argued in court that Trump was simply engaging in his First Amendment rights on January 6, that he did not incite an insurrection and that Section 3 was never meant to apply to presidential candidates.

They also contended that no single judge should end a candidacy based on an interpretation of a clause that has been used only a handful of times in 150 years.

“The petitioners are asking this court to do something that’s never been done in the history of the United States,” Mr. Trump’s attorney Scott Gessler said during closing arguments. “The evidence doesn’t come close to allowing the court to do it.”

The petitioners argued that there is little ambiguity in Section 3, which was mainly used before January 6 to prevent former Confederates from taking control of the government after the Civil War. 

It prohibits those who swore an oath to uphold the Constitution and then “engaged in insurrection or rebellion against the same” from holding state or federal office, unless granted amnesty by a two-thirds vote of Congress.

During a weeklong hearing earlier this month, they called a law professor who testified that the clause was widely understood to bar former Confederates from becoming president. He also showed post-Civil War documents indicating that even an act such as buying Confederate war bonds could make someone ineligible for office.

The attorneys seeking to knock Mr. Trump off the ballot contended he was simply disqualified, as plainly as if he failed to meet the 35-year age limit for the office. That this had never happened before was a reflection, they said, on Mr. Trump and his actions.

Legal historians say Section 3 fell into disuse after Congress granted an amnesty from its provisions to most former Confederates in 1872. It was revived after the attack on the Capitol, which was intended to stop Congress’ certification of President Biden’s win.

The case turned on 150-year-old records from the debate over the 14th Amendment. Judge Wallace said there is “scant direct evidence” that the measure was intended to apply to the presidency. 

She noted that Trump attorneys flagged a finding by one law professor that an early draft specified the presidency and vice presidency, yet the final version did not. The provision also refers to “officers of the United States,” a phrase that elsewhere in the Constitution does not include the top two offices.

Yet the petitioners’ legal historian testified that in the years after the Civil War it was widely understood that Section 3 would prevent Jefferson Davis, the former president of the Confederacy, from being elected president of the United States. 

The historian also unearthed records from the debate in which one senator asked if the measure applied to the presidency and an author read back the “officers of the United States” language. The senator who asked the question was then convinced that it did, indeed, include the president, according to the testimony.

“The record demonstrates an appreciable amount of tension between the competing interpretations, and a lack of definitive guidance in the text or historical sources,” Judge Wallace wrote.

The recent cases against Mr. Trump mark a new flurry of interest in the long-ignored provision that only started to gain attention after January 6.

The group that filed the Minnesota and Michigan challenges, Free Speech For People, also tried to remove two Republican representatives, Madison Cawthorn and Marjorie Taylor Greene, from the ballot in 2022 by citing Section 3. 

Mr. Cawthorn’s case became moot when he lost his primary, and a judge ruled against the lawsuit seeking to oust Ms. Greene.

CREW successfully used Section 3 to remove a rural New Mexico County Commissioner who entered the Capitol on January 6 and was later convicted of a misdemeanor.

Associated Press