We discussed this issue a bit during the Bivens discussion: What happens if state or local government enforces federal law. The answer, as we said briefly, is that it depends on how the officer was acting. A state or local official enforcing federal law for the state or locality is under color of state law and subject to § 1983. A state or local official working for the federal government acts under color of federal law and is subject only to Bivens.
This Ninth Circuit case addresses the issue as to two local law enforcement officers working for a joint task force created by federal law and supervised by federal officials.
