Yesterday’s excellent article by Ilya Somin in the Washington Post clearly explains the constitutional problems with the new president’s executive order on sanctuary cities:

• Supreme Court precedent mandates that the federal government may not impose conditions on grants to states and localities unless the conditions are “unambiguously” stated in the text of the law “so that the States can knowingly decide whether or not to accept those funds.” Few if any federal grants to sanctuary cities are explicitly conditioned on compliance with Section 1373. Any such condition must be passed by Congress, and may only apply to new grants, not ones that have already been appropriated. The executive cannot simply make up new conditions on its own and impose them on state and local governments. Doing so undermines both separation of powers and federalism.

• Section 1373 is itself unconstitutional. The Supreme Court has repeatedly ruled that the federal government may not “commandeer” state and local officials by ordering them to enforce federal law. Such policies violate the Tenth Amendment.