The most prominent issue in NFIB v. Sebelius was whether Congress’s regulatory power under the Commerce Clause stops at a point marked by a distinction between “activity” and “inactivity.” According to the law’s challengers, prior decisions about the scope of the commerce power already reflected the importance of the distinction between action and inaction. In all of the previous cases in which exercises of the commerce power had been sustained, the challengers argued, that power had been used to regulate activity. Never had Congress tried to regulate mere inactivity. In NFIB, four Justices rejected that contention, writing that such a distinction was previously unknown. Indeed, Justice Ginsburg described the idea of an activity/inactivity distinction as a limit on the commerce power as “a newly minted constitutional doctrine” conveniently engineered to declare the Affordable Care Act’s individual mandate unconstitutional.
Primus, Richard A. "The Most Revealing Word in the United States Reports." Green Bag 22, no. 4 (2019): 333-40.