Ray, you are thinking of the Supremacy Clause. But it does not apply to these types of laws. The Supremacy clause just says Fed Law Trumps state and local laws.

The Feds cannot force a State or Local agency to enforce Federal Laws. They are only sworn to enforce State and/or Local laws. In fact they cannot enforce federal Laws unless they are federally Deputized. All this lw would mean is that the locals won't enforce federal laws relating to that. It's legal and backed by case law.