This should be obvious to everyone, but sometimes the obvious is not so obvious.
We are a nation of States - the United States of America.
It is impossible for anyone to immigrate to the United States, legally or illegally, without immigrating to one of the states, i.e. one must be IN one of the states to be IN the United States.
The Constitution gives presumptive authority to the federal government to regulate immigration, but it does not give the federal government authority to regulate immigration in such a way that a particular state is harmed or benefited by such regulation, e.g. all immigrants with college degrees must live in Utah while all high school drop-outs must reside in Nevada.
Since the federal government has defaulted on it's responsbiility to control the southern border so that the states adjacent to that border receive the bulk of illegal immigrants, and bear the financial and crimminal burden of such unregulated immigration, the federal government is operating, de facto, to the harm of those states.
It is therefore, legitimate for the states suffering such harm to take action to relieve themselves from the burden incurred as a direct result of the federal government's failure to enforce federal laws. This does not give them authority to enact new immigration laws, but it does give them authority to enforce existing federal laws.
One would certainly not argue that if the federal government failed to repel an actual armed invasion by a foreign nation that the state/s suffering from such an invasion would be prohibited from acting to protect themselves (their citizen's lives and property) and repel the invastion.
