Immigration federalism describes:

1. Immigration federalism is the gradual movement of states into the immigration policy domain, an area traditionally handled by the federal government. 2. Since the late 1990s states have asserted a right to make immigration policy on the ground that they are enforcing, not supplanting, national immigration laws. 3. They have done so by restricting undocumented immigrants' access to education, health care and welfare benefits, areas within state responsibility. 4. States cannot negotiate treaties, which Article I, Section 10 forbids, and the naturalisation power remains an enumerated federal power. _Source: OpenStax American Government 3e (CC BY 4.0), Ch 3 "American Federalism", §3.4 Competitive Federalism Today_