POTUS won't allow the cities to descend into lawlessness.
he Insurrection Act of 1807 is a United States federal law (10 U.S.C. §§ 251–255)[1] (until 2016, found at 10 US Code, Chapter 15, §§ 331–335, renumbered to 10 USC, Chapter 13, §§ 251–255) that governs the ability of the President of the United States to deploy military troops within the United States to put down lawlessness, insurrection, and rebellion. The general purpose is to limit presidential power, relying on state and local governments for initial response in the event of insurrection. Coupled with the Posse Comitatus Act, presidential powers for federal military law enforcement on U.S. soil and unincorporated territories are limited and delayed.
https://en.wikipedia.org/wiki/Insurrection_Act