Subject: Re: USDollar
That case dealt with forcing state officials to run background checks for firearms under the Brady law, but the general principle is known as "Anti-Commandeering." Basically, the Supremacy Clause requires everyone (including state officials) to obey federal law, but the Tenth Amendment prohibits the federal government from requiring state officials to implement or enforce federal law, or to be "dragooned" into service to help the federal government enforce federal law. They can't make state officials administer background checks.

That's an entirely different matter to immigration enforcement!