The Ninth Circuit has long been the left-most federal appellate court in the United States. However, the day after Thanksgiving, the Ninth Circuit issued a decision that must have made President-elect Donald Trump very happy: It concluded that the Supremacy Clause means what it says, namely, that when it comes to the border, local political bodies cannot use regulations governing private parties to override the federal government’s supremacy on immigration matters. United States v. King County revolved around Boeing Field, an airport in King County, Washington (i.e., the Seattle area). In 1941, King County conveyed the field to the U.S....