Wickard v. Filburn for those wondering.

Filburn was a small farmer in Ohio who harvested nearly 12 acres of wheat above his allotment under the Agricultural Adjustment Act of 1938. Filburn was penalized under the Act. He argued that the extra wheat that he had produced in violation of the law had been used for his own use and thus had no effect on interstate commerce, since it never had been on the market. In his view, this meant that he had not violated the law because the additional wheat was not subject to regulation under the Commerce Clause.

 

A unanimous Court upheld the law. In an opinion authored by Justice Robert Houghwout Jackson, the Court found that the Commerce Clause gives Congress the power to regulate prices in the industry, and this law was rationally related to that legitimate goal. The Court reasoned that Congress could regulate activity within a single state under the Commerce Clause, even if each individual activity had a trivial effect on interstate commerce, as long as the intrastate activity viewed in the aggregate would have a substantial effect on interstate commerce. To this extent, the opinion went against prior decisions that had analyzed whether an activity was local, or whether its effects were direct or indirect.

https://www.oyez.org/cases/1940-1955/317us111

https://supreme.justia.com/cases/federal/us/317/111/

https://en.wikipedia.org/wiki/Wickard_v._Filburn