The Colorado Supreme Court on Tuesday disqualified former President Donald Trump from appearing on the state’s 2024 presidential ballot under the Constitution’s insurrection clause, a shock ruling that may have far-reaching implications for the Republican frontrunner.

The decision, which reversed an earlier ruling by a lower court in Colorado, was put on hold until Jan. 4 pending appeal. A spokesperson for the Trump campaign said it plans to appeal to the Supreme Court, calling the ruling a “deeply undemocratic decision.”

Activists have been pushing for Trump to be blocked from the 2024 ballot under the 14th Amendment, which says officials who “engaged in insurrection” are barred from holding office.