What he is referring to has nothing to do with constitutional law -- Obama, the legal scholar, forgot to ensure there was a severability clause included in his legislation. Therefore, should federal court find for any of the states' actions then the entire legislation is void.
One has to wonder if the Democratic Congress is collectively sighing in relief over this news.
I wouldn't, because at the end of the day, this will still take several years at least until this is wrung out. And even if the bill is rendered moot in its entirety, the damage with the increased taxes has already been done. Plus, people are going to remember not that the bill went away, but that certain people voted for it in the first place, and given the chance, would do so again.