2. CHIEF JUSTICE ROBERTS concluded
in Part III–A that the individual
mandate is not a valid exercise of Congress’s power under the
Commerce Clause and the Necessary and Proper Clause. Pp. 16–30.
(a) The Constitution grants Congress the power to “regulate
Commerce.” Art. I, §8, cl. 3 (emphasis added). The power to regulate
commerce presupposes the existence of commercial activity to be regulated.
This Court’s precedent reflects this understanding: As expansive
as this Court’s cases construing the scope of the commerce power have
been, they uniformly describe the power as reaching “activity.” E.g.,
United States v. Lopez, 514 U. S. 549, 560. The individual mandate,
however, does not regulate existing commercial activity. It instead compels
individuals to become active in commerce by purchasing a product, on the
ground that their failure to do so affects interstate commerce.....