Washington | The Colorado Supreme Court has ruled that Donald Trump cannot run for president next year in the state because of his role in the attack on the US Capitol in 2021 and ordered the exclusion of his name from the state's Republican presidential primary ballot.

The disqualification of the 77-year-old former president on Tuesday was based on the Constitution's 14th Amendment, which says officials who take an oath to support the US Constitution are banned from future office if they "engaged in insurrection." Trump is currently the front-runner in the Republican Party's nomination process for the race for the White House in 2024. Trump's campaign has vowed to appeal against the "flawed" ruling by the Supreme Court of Colorado in the US Supreme Court.

The Colorado Supreme Court upheld a trial judge's decision that Trump engaged in the January 6, 2021, insurrection and also overturned her conclusion that the ban does not apply to the presidency.

The landmark decision from the divided top state court marks the first time a court has found Trump ineligible to return to the White House due to his conduct surrounding the January 6, 2021, attack on the US Capitol, CBS News reported.

Never before has a court determined that a presidential candidate is disqualified under the Civil War-era provision clause, it said.

The state high court stayed its ruling until January 4 — a day before the deadline for the state secretary to certify the candidates for Colorado's March 5 primary election.

The 4-3 ruling by the seven-member Colorado Supreme Court does not apply outside of the state.

"President Trump's direct and express efforts, over several months, exhorting his supporters to march to the Capitol to prevent what he falsely characterised as an alleged fraud on the people of this country were indisputably overt and voluntary," the justices wrote.

"Moreover," they wrote, "the evidence amply showed that President Trump undertook all these actions to aid and further a common unlawful purpose that he himself conceived and set in motion: prevent Congress from certifying the 2020 presidential election and stop the peaceful transfer of power." "[W]e conclude that because President Trump is disqualified from holding the office of President under Section Three, it would be a wrongful act under the Election Code for the Secretary to list President Trump as a candidate on the presidential primary ballot.," the ruling stated.

The ruling follows a months-long challenge in the state to the former president's ballot eligibility under Section 3 of the 14th Amendment, which deems former office-holders ineligible from running again if they took an oath to support the Constitution and then engaged in "insurrection or rebellion" against the US.

The ruling also denied Trump's appeal on 11 issues and found that his actions on January 6, including a speech outside the White House that morning, were not protected by the First Amendment free speech protections, ABC News reported.

Trump has denied wrongdoing regarding the January 6 insurrection and has decried the 14th Amendment lawsuits as an abuse of the legal process. He is under federal and state indictment in connection with his attempts to overturn the 2020 election won by Joe Biden, a Democrat, and he has pleaded not guilty.

Trump has attacked the Colorado 14th Amendment challenge -- and similar such lawsuits against him around the country -- as baseless and anti-democratic.

A Trump spokesman has vowed an appeal and said that the campaign has already begun fundraising off of the decision.

"The Colorado Supreme Court issued a completely flawed decision tonight .... We have full confidence that the US Supreme Court will quickly rule in our favour and finally put an end to these unAmerican lawsuits," spokesman Steven Cheung said in a statement, according to US media reports.

Representatives for President Biden's re-election campaign declined to comment on the Colorado ruling. But a senior Democrat affiliated with the campaign told CBS News that the decision would help Democrats by supporting their argument that the US Capitol riot was an attempted insurrection.

Trump lost the state of Colorado by a wide margin in the 2020 presidential election. But if courts in more competitive states followed suit on Tuesday's ruling, Trump's White House bid in 2024 could face serious problems.

Trump has so far faced multiple 14th Amendment challenges in various states. Lawsuits citing the 14th Amendment were dismissed by nine courts: in Michigan, by the district court in Colorado -- leading to the appeals battle there -- and by the Minnesota Supreme Court, a district court in Washington and federal courts in Arizona, Rhode Island, New Hampshire and Florida, the reports said.