Having not read the court’s decision, I wondered whether the penalty having been justified as a tax meant that it could be challenged in the future under the Anti-Injunction Act of 1867 but not until after the tax had been collected. Seems to be a “don’t holler til your’e hurt” law as my mom would have said. If that were the case, all the Roberts’ opinion was saying was that the case was not ripe: that it had been brought prematurely. I am not that learned in the law, this was brought up in a Washington post article that I read several months ago.
But it turns out that Roberts dealt with that. He actually did not rule that it was a tax, just that it was like one. A nuance that seems to have been lost in most of the reporting. Interesting article from Politifact contains an explanation: