At what point do the states regain their sovereignty then if they can be treated as a federal enforcement agency? We might as well do away with the idea of states altogether then.
So, we come full circle, if states aren't required to cooperate with the government in enforcing immigration law, we don't need borders. If states are required to cooperate with government enforcement of immigration law, there needn't be states either.
At what point does the government regain the plenary right to enforce its sovereign borders, if it can't enforce its own laws in the way the Constitution requires it to? We might as well do away with the idea of national sovereignty altogether as well, and allow the states to get away with obstruction of justice.
If the country can't enforce its borders, there needn't be a country. What good are states if the nation they are apart of can't enforce its sovereignty? Borders mean nothing, thus the borders between states are rendered meaningless as well. No sovereign border, no state borders, no nothing. All of it goes away.
The fact that states shouldn't be forced to cooperate with the Government in enforcing immigration law essentially renders the government helpless to do its constitutionally mandated duty.