The Colorado Supreme Court ruled last month that the former president could not appear on the state’s Republican primary ballot because he had engaged in insurrection.

The case turns on the meaning of Section 3 of the 14th Amendment, ratified after the Civil War, which bars those who had taken an oath “to support the Constitution of the United States” from holding office if they then “shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof.”