The US Supreme Court on Thursday heard arguments in former President Donald Trump's battle to avoid being kicked off state presidential ballots for his involvement in the 2021 Capitol attack. 

Colorado's top court had disqualified Trump from the state's Republican primary ballot under the US Constitution's 14th Amendment after it found that he had participated in an insurrection.

Dozens of demonstrators gathered outside the courthouse, some holding signs reading, "Failed Coup," "Remove Trump" and "Trump is a Traitor." Police set up barricades around the white marble building for security.

What is the court being asked to decide?

The nine justices must rule whether Trump is ineligible to appear on the primary ballot in Colorado.

Colorado's Supreme Court in December ruled that Trump should not be allowed to stand because of his role in an insurrection — the January 6, 2021 assault on the US Capitol by his supporters.

Section 3 of the 14th Amendment stops anyone holding public office if they engage in "insurrection or rebellion" after having previously pledged to support and defend the Constitution.

The amendment was ratified in 1868 after the Civil War to prevent supporters of the slave-holding secessionist Confederacy from being elected to Congress or holding federal positions.

Judges concerned about state overreach 

The justices spent time considering the proper way that states may enforce the provision, with a focus on whether the US Congress must first pass legislation.

Both sides of the political spectrum expressed concern about individual states having the power to influence a national election.

Conservative Chief Justice John Roberts warned that if the Colorado decision is upheld, it could set a precedence for other states to disqualify candidates.

"And it will come down to just a handful of states that are going to decide the presidential election. That's a pretty daunting consequence," Roberts said.

Justice Elena Kagan, who was nominated to the top court by Democrat Barack Obama, remarked that the decision of the Colorado Supreme Court to remove Trump from the ballot " could effectively decide this question for many other states, perhaps all other states."

"Why should a single state have the ability to make this determination not only for their own citizens but for the rest of the nation?" she added. 

The Colorado appeal is the most consequential election law case to be considered by the country's highest court since it stopped the Florida vote recount in the 2000 US presidential election with Republican George W. Bush narrowly ahead of Democrat Al Gore.

What Trump's team has said

Representing Trump, former solicitor general of Texas Jonathan Mitchell opened the scheduled 80 minutes of oral arguments and said that only Congress could disqualify a candidate.

"The Colorado Supreme Court's decision is wrong and should be reversed for numerous independent reasons," Mitchell said, adding that it would "take away the votes of potentially tens of millions of Americans."

In a brief to the court, Trump's attorneys had said that the "American people — not courts or election officials — should choose the next President of the United States."

 "At least 60 states and federal courts throughout the country have refused to remove President Trump from the ballot," they said. "The Colorado Supreme Court is the lone outlier."

Trump's team said the amendment could only be enforced through "congressionally enacted methods" and not through the state courts. They also said the former president "did not 'engage in' anything that constitutes 'insurrection.'"

Trump faces four separate criminal cases; over allegations that include mishandling classified documents, seeking to overturn 2020 election results, and paying a porn star to cover up an affair.

wmr,rc/wd (AP, Reuters, AFP, EFE)