I think like TF this is a pretty easy argument, but think who's "interpreting." After all is said and done, the SupCt will not let this fly, simply because it's less money to the federal coffers. You can bet they somehow rig it to be a 'federalist' decision, too.
I just read up a bit more on the law. It is worded so that a person in each state may deduct either their sales or income tax, whichever is higher. This will certainly pass constitutional muster.