My brother and I were discussing the constitution today and I told him that the Laws (and treaties) passed by the government, as long as they were in pursuance of the constitution, were supreme laws of the land. Therefore, the government’s laws that were unconstitutional could essentially be nullified by the States. However, he then asked me what would happen if the States completely violated the constitution, and his example was if a State, after the ratification of the 13th amendment, decided years down the line to ignore this amendment and enslave a particular group of people. What could the central government do, or what would be the solution to that particular kind of problem, where a State violated an amendment that was pretty black and white? I didn’t have a very sound answer for his question. Other than to suggest, jokingly, there would be another Civil War.
This is why federal courts exist. The short of it is that such a statute would be enjoined immediately, and anyone who attempted to implement it would be sent to jail for contempt of court. Resistance to such attempts would have outcomes such as at Little Rock in 1957, Oxford in 1962, and Tuscaloosa in 1963; in each of those cases–the first one involving the US Army, governors backed down rather than go to jail.