The Supreme Court’s decision on Friday in Fischer v. U.S. struck down one of the most common charges against January 6 defendants. “Obstruction of an official proceeding” had been used in hundreds of cases, and those convictions are now invalid. But the biggest impact of the decision may occur elsewhere. For years, calling January 6 an “insurrection” has been a litmus test for press, pundits and politicians. Members of Congress such as Eric Swalwell (D-Calif.) claimed a conspiracy of “armed and organized insurrectionists.” The claim is legally absurd but politically advantageous. It now seems like the insurrection increasingly looks more...