The Colorado supreme court has ruled that Donald Trump is ineligible to run for the White House again, citing his role in the January 6 attack, in a ruling that could have major reverberations for the 2024 election.

The decision removes Trump from the state’s Republican presidential primary ballot, and stems from a rarely used provision of the US constitution known as the insurrection clause.

Here’s what we know so far, and what it might mean for the former president and current Republican frontrunner.

What is the insurrection clause and why was it used?

The decision by the Colorado supreme court is the first time a candidate has been deemed ineligible for the White House under the US constitutional provision.

Section 3 of the 14th amendment, also referred to as the insurrection clause, bars anyone from Congress, the military, and federal and state offices who once took an oath to uphold the constitution but then “engaged” in “insurrection or rebellion” against it.

Ratified in 1868, the 14th Amendment helped ensure civil rights for formerly enslaved people, but also was intended to prevent former Confederate officials from regaining power as members of Congress and taking over the government they had just rebelled against.

A growing number of legal scholars say the post-civil war clause applies to Trump because of his role in trying to overturn the 2020 presidential election and obstruct the transfer of power to Joe Biden by encouraging his supporters to storm the US Capitol.

“The dangers of Trump ever being allowed back into public office are exactly those foreseen by the framers of section 3,” Ron Fein, the legal director for Free Speech for People, told the Guardian in a recent interview. “Which is that they knew that if an oath-taking insurrectionist were allowed back into power they would do the same if not worse.”

How did this happen?

The decision on Tuesday marks a victory for advocacy groups and anti-Trump voters, who have mounted similar legal challenges to Trump’s candidacy, citing the insurrection clause.

The case was brought by a group of Colorado voters, aided by the group Citizens for Responsibility and Ethics in Washington, who argued Trump should be disqualified from the ballot for his role in the January 6 attack.

The decision from Colorado’s highest court overturned an earlier ruling from a district court judge. That judge found Trump’s actions on January 6 amounted to inciting an insurrection but said he could not be barred from the ballot, because it was unclear that the clause was intended to cover role of the presidency.

Has this happened before?

The provision has almost never been used and not in such a high profile case. In 1919, Congress refused to seat a socialist in Congress, contending he gave aid and comfort to the country’s enemies during the first world war.

Last year, in the provision’s first use since then, a New Mexico judge barred a rural county commissioner who had entered the Capitol on January 6 from office under the clause.

According to the provision, a disqualification from office can be overturned “by a vote of two-thirds of each House”.

What does this mean for the election?

So far, the Colorado ruling applies only to the state’s Republican primary, which will take place on 5 March, meaning Trump will not appear on the ballot for that vote.

But its conclusion would likely also affect Trump’s status in the state for the general election ballot on 5 November.

Furthermore, the ruling could influence other cases across the US, where supreme courts in Minnesota and Michigan, a key battleground state, are considering similar arguments.

Advocates have hoped to use the case to boost a wider disqualification effort and potentially put the issue before the US supreme court.

Has Trump responded yet?

Trump didn’t mention the decision during a rally Tuesday evening in Waterloo, Iowa, but his campaign sent out a fundraising email citing what it called a “tyrannical ruling”.

His attorneys, meanwhile, have argued that the 14th amendment’s language does not apply to the presidency and promised to appeal any disqualification immediately to the US supreme court, which has the final say in constitutional matters.

A lawyer for Trump has argued that the January 6 riot at the Capitol was not serious enough to qualify for insurrection and that any remarks that Trump made to his supporters that day in Washington were protected under free speech. The lawyer contended that courts do not have the authority to order Trump removed from the ballot.