If the state and local authorities fail to provide this (like allowing slavery to continue for example), the federal government has the right and the obligation to step in.
This was further codified in the Insurrection Act.
From History.com:
In 1861, Abraham Lincoln expanded the law to form the legal basis for waging the Civil War. Without it, he wouldn’t have had the authority to send federal troops into a state without the governor’s permission.
After the Civil War, the Insurrection Act was further amended to give the president authority to enforce the 14th Amendment and the conditions of Reconstruction in the South. That authority is now found in Section 253 of Title 10 of the U.S. Code, which gives the president the right to take military action within a state when “any part or class of its people is deprived of a right, privilege, immunity, or protection named in the Constitution and secured by law, and the constituted authorities of that State are unable, fail, or refuse to protect that right, privilege, or immunity, or to give that protection.”
That’s the same authority invoked during the civil rights era by Presidents Eisenhower, John F. Kennedy and Lyndon Johnson to deploy troops to the South to enforce desegregation in defiance of the governors of Arkansas, Mississippi and Alabama.
The Insurrection Act was last invoked in 1992 under President George H.W. Bush, after Peter Wilson, then-governor of California, requested help to quell widespread riots after four police officers charged in the beating of Rodney King were acquitted.
I do NOT believe that POTUS will have to implement the Insurrection Act, but of course, he can if he wants.
I believe that is what DemonRats are hoping he will do to go along with their Trump is a Dictator. POTUS will out smart them and get the job done anyway. Special Ops may well go in and snag the provocateurs/leaders or something.