I suppose but agents take their marching orders from the director of the Secret Service, not the President. Any agent willing to disregard the law - specifically, not allowing another law enforcement officer to conduct his lawful duties - is, at best, throwing away his career as no other agent will ever work with someone who doesn’t respect the chain of command and the law. At worst, said agent is also arrested as a criminal.
If I worked for the Secret Service, I’d be more concerned with staying employed and keeping a clean record. Politicians are temporary but career civil servants can have lifetime employment.
Every day is new historical territory with this presidency but the whole checks-and-balances thing keeps Trump’s most fascistic impulses cornered. He can’t even get his centerpiece campaign promise, a wall with Mexico, funded.
