The Insurrection Act, Chapter 13 of Title 10 (10 USC Sections 251-255). This act allows the President to use U.S. military personnel at the request of a state legislature or governor to suppress insurrections. It also allows the president to use federal troops to enforce federal laws when rebellion against the authority of the U.S. makes it impracticable to enforce the laws of the U.S. by the ordinary course of judicial proceedings.

https://www.northcom.mil/Newsroom/Fact-Sheets/Article-View/Article/563993/the-posse-comitatus-act/fbclid/IwAR0sCaTedntLw2-Tj4bDpNheBlipoP5w-EcsWm0qP6Gzf4EZ58spNqHUo44/