Despite a ruling in Colorado that found Donald Trump can remain on the 2024 ballot even though his actions on Jan. 6 effectively made him an insurrectionist, a law professor from the University of Notre Dame has filed a legal brief citing past cases that blocked presidential candidates from the vote, Newsweek reported.

Derek T. Muller cited the 1968 case of former Black Panther leader Eldridge Cleaver who ran for president for the Peace and Freedom Party. California excluded Cleaver from the ballot because he was below the 35-year-old minimum age limit for the presidency — despite arguments that he would reach the age while in the post.

"Cleaver was the 33-year-old nominee of the Peace and Freedom Party. He challenged the exclusion in state court, which rejected his challenge. Cleaver petitioned for certiorari to the United States Supreme Court. Without comment, the Court rejected the petition," Muller wrote.

According to Muller, Cleaver's case "demonstrates the fact that a state did exclude a candidate from the ballot for failure to meet the qualifications for office. And intriguingly, California excluded Cleaver even though Cleaver would become eligible during the four-year [presidential] term of office."

"[Trump] has argued that states have no power to judge the qualifications of candidates or that it is a political question. The historical record however suggests that in at least some cases, states have excluded candidates," Muller told Newsweek.

The Colorado decision — currently being appealed — ruled that Trump did take part in an insurrection, but the 14th Amendment clause that bars insurrectionists from taking public office does not apply to presidents.

But similar 14th amendment challenges in several other states have failed because judges have ruled its up to Congress, and not the states, to disqualify.

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"States routinely exclude ineligible candidates. In 2008, for instance, Róger Calero, a Nicaraguan national, was the Socialist Workers Party nominee for president. In some states, Calero's name appeared on the ballot. In others, a stand-in candidate, James Harris, appeared in Calero's place in states where Calero was excluded from the ballot," he wrote in his briefing.

District Judge Sarah B. Wallace allowed Trump to say on the Colorado ballot because it was unclear whether a Civil War-era constitutional amendment that barred insurrectionists from public office applied to the presidency.

Muller acknowledged that the odds of the Colorado Supreme Court excluding Trump from the ballot are low.

"There are a number of things that the Colorado Supreme Court must find to exclude him from the ballot, but any one thing in Trump's favor can keep him on," Muller said.

Read more at Newsweek.