Subject: Re: USDollar
Which they're allowed to do under the Constitution

Says who? Localities do not make national immigration policy. To my recollection Sanctuary City laws haven't been fought out in front of the Supreme Court.

What that means is that the States do not exist to serve the federal government's purposes, and thus cannot be "commandeered" to use their resources to enforce or promote compliance with federal law. They have to follow federal law, but they can't be forced to serve as an instrumentality of the federal government.

This very thin gruel but I understand the legal argument being made here (which is around who can compel resources to do what in what scenario).