It was part of Scalia’s argument in dissent on the soveignty of states, so he wasn’t concerned with impeachment but in establishing that the power to decide who can or can’t enter your territory is the primary definition of sovereignty.
Yes, but isn't federal sovereignty in regard to this issue already well-established by the Constitution and SC precedent? Didn't Arizona take pains to ensure that there was no conflict with federal law? Is he advocating a system of parallel state laws mirroring federal laws? Lack of enforcement of federal law is at the root of the illegal invasion. Obama refuses to enforce federal law.