Some people think Roberts cleverly used this case to severely limit Congress’s regulatory powers. Others strongly disagree.
I’m with the others.
I think that as a practical matter, this will have almost no limiting effect at all on Congress’s regulatory powers. I can’t think of any circumstance in which this limitation would apply and in which there would be no other enumerated power under which Congress could enact the law. In this case, the other enumerated power is the taxing power. In the case of, say, the Selective Service Act, the enumerated power is the power to provide for the national defense. Etc.
The reason that this limitation is insignificant is that the Commerce Clause argument was really a disguised Fifth Amendment due process (liberty! broccoli!) argument, and Roberts flatly rejected that. He said, no, the Commerce power doesn’t allow this but the taxing power does—and, no, it doesn’t violate fundamental constitutional concepts of freedom, of liberty! There may be other things that could be compelled under the taxing power—broccoli purchases, maybe—that would violate Fifth Amendment due process concepts (freedom! liberty!) and thus be unconstitutional on that basis, just as there are things that could be compelled under the Commerce power that would violate that concept of due process and thus be unconstitutional on that basis. But this does not violate that concept of due process (freedom! liberty!).
No, Roberts didn’t specifically separate the two concepts—Commerce Clause limitations and Fifth Amendment due process—and, yes, he does almost seem to conflate them the language Scocca quotes. But the bottom line is that he found no due process (freedom! liberty!) problem with the mandate and penalty, and therefore no slippery slope to broccoli in this instance, even though he says the Commerce power isn’t broad enough to authorize the statute.