The Bunker Group
Plus there is the posse comitatus act which significantly restricts how the US military can be used internally. I seem to remember there was even some rumblings about using them in disaster relief type operations because of that, so suppressing civil strife would certainly be an issue. I know that Lincoln did something like that at the start of the civil war under the Insurrection Act, but even then (from memory) it was considered to be of doubtful legality and that was before Hayes signed 18 USC 1385. It doesn't directly apply to the Navy and Marines, but from memory there is some sort of equivalent for them.