Jim.
I believe this was an ex post facto law. That it did indeed make something illegal after the fact. However I also believe that any compact between two parties need both to nullify it. Secession should have been fought out in congress. I do like BB's thought though. Let Texas vs. White be challenged. Let Constitutional lawyers debate it. Every side heard. It is indeed the eternal argument. As for slavery Jim. Both you and I had ancestors who fought on both sides. I doubt that the defense of slavery or abolishing it was the issue for them. It was how this country was perceived...federal (small f) or national. Thing is, Madison (who knew a little about the Constitution) said it was both. Yes Jim, by it's very nature it is the eternal argument.
Cump.