At the New York Times they’re debating whether the federal government has the authority to compel state and local governments to enforce federal immigration law. You can read the pro and con positions if you care to.
My own view is that the federal government (meaning the executive branch of government) does not have the authority to compel city governments. The Congress could withhold funding from cities as motivation but it can’t just order them to do things.
State governments, however, have plenary authority over the cities incorporated under their statutes. State legislatures’ diktats could compel those cities to do their will. Governors could send the National Guard to arrest mayors and other city officials if they don’t comply and it probably wouldn’t even require a court order, although there may be some due process considerations.
However, I think the position of the sanctuary cities is foolish and self-destructive in part for the reasons outlined in the pro argument at the NYT—it’s an interference in ordinary inter-agency law enforcement. I also think that it undermines the legitimacy of government more generally.
Furthermore, I think that, if city governments believe that the interests of residents who don’t obey our laws override the interests of tax-paying citizens who do, they have much larger problems than the federal government.
Notice the shift here, a few years ago the debate was whether Arizona could enforce federal immigration law. As I recall the answers from the courts was a bit mixed, but the main issue was identifying the line where Arizona was interfering with federal enforcement prerogatives.
Now, the question is how can the federal government compel state and local government to help enforce immigration laws. And I think the obvious answers are making financial subsidies available to encourage voluntary participation. The other is to condition federal benefits on immigration screenings and reporting, but as Justice Roberts argued in the ACA case, the federal government cannot condition pre-existing benefits with new obligations, so this would apply to situations where legal status was already required. The Constitution also guarantees illegal immigrants primary and secondary education, so this area would not be fruitful.
One thing I was wondering about was the Universities are taking the position that they will not help identify undocumented aliens. When I was in high school, Reagan reinstated the requirement that young men register for the draft, and this was enforced by conditioning federally-backed student loans and grants. I wasn’t in favor of it, but there was realistically no way for me to go to college without registering. I don’t know if the colleges were involved at all in enforcing this requirement, or it was simply a matter of me filling out a form that the feds reviewed. I’m not sure how this is any different.