In a landmark decision, the Colorado Supreme Court has ruled that former president Donald Trump is disqualified from appearing on the state’s primary ballot next year.

The Justices’ 4-3 ruling concludes that Trump engaged in an insurrection with his words and actions around the January 6th attack on the U.S. Capitol and therefore cannot hold the nation’s highest office again.

“We are also cognizant that we travel in uncharted territory,” wrote Colorado’s Supreme Court in its unsigned 213-page decision.

This is the first time a state’s high court has concluded the 14th Amendment’s Civil War-era Disqualification Clause applies to both the office of the presidency and the actions of the former president. Supreme Courts in Minnesota and Michigan dismissed similar complaints.

“We do not reach these conclusions lightly,” wrote the Justices. “We are mindful of the magnitude and weight of the questions now before us. We are likewise mindful of our solemn duty to apply the law, without fear or favor, and without being swayed by public reaction to the decisions that the law mandates we reach.”

In a statement, the Trump campaign called the ruling “a completely flawed decision” and said it would swiftly file an appeal to the United States Supreme Court.