What Chief Justice Roberts substituted for that—what he called a “saving construction,” which he admitted was not the best reading of the text—was a tax power, but not the tax power that law professors have been advocating. Law professors said, “You could just do this whole thing under the tax power. You could just call it a tax; it’d be the same.” But that’s not what he said. He said, “Well, it’s written like a tax, if you take the requirement out. First of all, you’ve got to take the requirement out.” There was a requirement that everybody buy insurance. You’ve got to take that out because that’s unconstitutional under the Commerce Clause. So [if] you take the requirement out, what you’re left with is the penalty. And the penalty, he said, is so low that it could actually be a tax and not a penalty.
He said the mandate was not a penalty because it was so low. If it had been higher, it might have been a penalty, and it would have been unconstitutional because it would be coercive. What he really said was that Congress can tax inactivity as long as those taxes allow people to make a choice. But if that monetary exaction, he said, ever got so punitive that it would be coercive, in that case it would be a penalty and it would be unconstitutional—he implied that it would be unconstitutional; that wasn’t before him.
So he substituted a less dangerous tax power for a far more dangerous Commerce Clause power. If the Commerce Clause power had been upheld, not only would the enumerated powers scheme have gone away, but Congress could have changed the law to punish this or any future mandates by very extensive penalties, like high fines and even imprisonment.