District Court Judge Francis Mathew found that Couy Griffin, a former county commissioner and founder of the group Cowboys for Trump, had participated in the violent U.S. Capitol attack on Jan. 6, 2021. Mathew invoked a nearly forgotten part of the 14th Amendment, called Section 3, which can disqualify certain people from state or federal office if they have “engaged in insurrection or rebellion” or given “aid or comfort” to the United States’ enemies. The clause was first adopted after the C...