My friend LT asks me how the states can enforce the 10th Amendment today (truthfully, he asked me weeks ago and I forgot that I hadn't answered him). It seems tricky and difficult, but there are ways in which state governors and legislatures can begin to push back against the federal leviathan. I am no lawyer, but here's my first thoughts on the matter:
The first step is what several states have already done, which is to formally inform the federal behemoth that they are taking back there constitutional powers in the areas in which the federal government has unconstitutionally intruded itself. The next will be to pass legislation to forbid any government entity in the state from co-operating in the enforcement or implementation of any unconstitutional federal mandate. (Please note that I do not mean to imply that the so-called "sanctuary cities" actions would be justified by this process. The securing of our nations borders and dealing with those who enter illegally is a proper federal function.)
The next step would be trickier. It would involve refusing to send any money to the federal government to be used for unconstitutional purposes. This would involve calculating how much of the money collected in a state goes to these purposes, in proportion to the total federal levies collected. Then these funds should be embargoed, ideally to be returned to the taxpayers. (Yes, I can hear you saying "good luck with that".) I suppose a case could be made that some of the funds might be held for the state to use to fight the inevitable court battle.
As I said, I'm no lawyer. These are just my humble thoughts on the matter. None of this would be easy. Of course, rebelling against the most powerful nation on earth wasn't easy, either, but a few thousand scrappy, idealistic patriots pulled it off over 200 years ago.
If we do not try, we will never succeed.