The State's Anti Common During Principle

A lot of it surrounds essentially what's called an anti common during principle, which is this idea that the states cannot be sort of conscripted into enforcing federal law. It most recently has come up in cases where a federal government might say, okay, we're doing background checks for a certain type of weapon or something. The Supreme Court says, well, you can't do that because you're forcing state officials to implement federal enforce federal law.