The court ruling explicitly stated that the statute could not stand under the Commerce Clause.

You could probably argue that some of the other things in the ruling very strongly suggest that the Court didn't understand the scope of the statute and the impact of invalidating the statute as a whole and might have said something different if it was reasoning clearly, but even though it might be a result you favor in this case, I doubt you really want executive agencies to start applying court decisions based on what they think the court would have ruled had it been reasoningly clearly rather than what the court actually ruled.