The President Has the Constitutional Power to Restore Order. He Must Act.
(excerpt)
Under Article IV of the Constitution, the United States guarantees every state a republican form of government, protection against invasion, and — on request of the state government — protection from domestic violence. In furtherance of this provision, Congress enacted legislation, most notably, the Insurrection Act of 1807, which empowers the president “to suppress, in any State, any insurrection, domestic violence, unlawful combination, or conspiracy.” Obviously, suppressing such attacks requires deploying the United States armed forces as needed.
https://www.nationalreview.com/2020/05/the-president-has-the-constitutional-power-to-restore-order-he-must-act/?amp