We used to argue this question in law school. I took the position that NBA players were allowed to commit six fouls, and college players five. My argument was that, while you would pay a significant price for committing the sixth foul (or the fifth in college), namely having to sit out the rest of the game, the rules did not bar you from committing it. If you were on the court and elected to commit it, no one would stop you.
The students I argued with said that NBA players were only permitted five fouls (college players four) because any additional fouls would be harshly penalized in a way that earlier fouls were not. In this sense, players were prohibited from committing the “fatal” foul.
I can’t remember whether I actually believed my position or took it just for the sake of arguing. I’m pretty sure I thought that both views were defensible, and that arguing the matter was fun but not at all consequential.
A similar dispute, though not an identical one, appears to lie at the heart of the highly consequential debate between Chief Justice Roberts and Justice Kennedy over whether it is “fairly possible” to view the payment that must be made under Obamacare for not purchasing health insurance as a tax. Roberts’ view that it reasonably can be considered a tax rests, at least on part, on the claim that there is no prohibition against not buying health insurance. An individual can refuse to buy insurance, just as a basketball player can commit that last foul, though he or she will pay a price for the refusal.
Kennedy’s view is that the price one must pay for not purchasing insurance entails a prohibition. He quotes the great jurist Chancellor Kent as follows: “If a statute inflicts a penalty for doing an act, the penalty implies a prohibition, and the thing is unlawful, though there be no prohibitory words in the statute.”
Kennedy’s view of this matter is more persuasive than the Chief Justice’s. But remember, under rules of constitutional adjudication, Roberts’ view need not be the most persuasive one. As Kennedy concedes, it must only be “fairly possible.”
Unfortunately, the “fairly possible” test is a squishy one, to say the least. In the end, its application can depend on the lengths to which a judge is willing to go to avoid overturning a legislative act. Chief Justice Roberts went to considerable lengths, and is vulnerable to the criticism that he went too far.