I'm thinking it may not be as rare any longer.
I'm not arguing that he "can't" do this, I'm stating that I think it may cause his own plans problems, and that he probably should think it through a bit more before doing such things. If ObamaCare doesn't get a ruling from the SCOTUS during his Presidency I see the next guy using it almost immediately. Until now is my prediction.
I think you are missing the question for the forest of "law" and the awesome "precedent" of ignoring supposedly unconstitutional law. First, he isn't ignoring this law, it is still in place.
I would not call it rare, and this precident aint going to stop the next guy from trying it should he choose.
I suspect the next guy will be a liberal democrat, so I doubt he will try it on HealthCare. I also suspect that the hart of America knows the HeathCare Bill is MUCH better than where we were with HeathCare that not defending the law would be a very unpopular position to take.