In theory, the actual individuals are still bound by state law, but the supremacy clause allows federal laws made in pursuance of the US Constitution to preempt those state laws. Of course, these laws still need to be "necessary and proper" for carrying out an express power like regulating immigration. A law that is unnecessary or improper would theoretically not hold up in court. The same goes for executive action.

Perhaps the most infamous case of this was the Idaho manslaughter case against FBI sniper Lon Horiuchi for killing Vicki Weaver in the Ruby Ridge incident. His case was simply "removed" to federal court and dismissed under the supremacy clause (although this dismissal was later overturned narrowly when appealed).

What ever happened to "States Rights!"?

the real rub comes when someone tries to restrict the movements of federal "agents" into or within the state.

> They're just going say that they're federal and not bound by state law

Sure. But hopefully they'll be saying that while one of their own is being charged.

Federal agents are 100% bound by State laws. Unless there is a Federal law that overturns the state law, Federal agents absolutely have to obey.