"Long before the uprising at the Capitol, the threat of insurrection has held a mirror to America's highest ideals and deepest fears. The Insurrection Act of 1807-passed amid pervasive fears of slave rebellion-authorizes the president to deploy federal troops to quell domestic uprisings. Invoked during Reconstruction and the civil rights movement, the Act was deployed to enforce the promise of equal citizenship for Black Americans. But the Act has...