Clarence Thomas appears to have set out to agree with the Opinion of the Court and to also write a short note arguing that Congress's power to regulate interstate commerce does not extend to "economic activity [that] substantially affects interstate commerce."
When the Scalia opinion became the Scalia dissent, Thomas forgot to change the first "joint opinion" to "joint dissent"--although he did change the second "joint opinion" to "joint dissent".
I dissent for the reasons stated in our joint opinion, but I write separately to say a word about the Commerce Clause. The joint dissent and THE CHIEF JUSTICE correctly apply our precedents to conclude that the Individual Mandate is beyond the power granted to Congress under the Commerce Clause and the Necessary and Proper Clause. Under those precedents, Congress may regulate “economic activity [that] substantially affects interstate commerce.” United States v. Lopez, 514 U. S. 549, 560 (1995). I adhere to my view that “the very notion of a ‘substantial effects’ test under the Commerce Clause is inconsistent with the original understanding of Congress’ powers and with this Court’s early Commerce Clause cases.” United States v. Morrison, 529 U. S. 598, 627 (2000) (THOMAS, J., concurring); see also Lopez, supra, at 584–602 (THOMAS, J., concurring); Gonzales v. Raich, 545 U. S. 1, 67–69 (2005) (THOMAS, J., dissenting). As I have explained, the Court’s continued use of that test “has encouraged the Federal Government to persist in its view that the Commerce Clause has virtually no limits.” Morrison, supra, at 627. The Government’s unprecedented claim in this suit that it may regulate not only economic activity but also inactivity that substantially affects interstate commerce is a case in point.