In which case did the Supreme Court rule that Congress could not regulate a trust controlling 98% of sugar manufacturing?

The ruling in United States v. E.C. Knight Co. is significant because it established a pivotal interpretation of the Sherman Antitrust Act regarding the extent of Congress's regulatory powers over interstate commerce. In this case, the Supreme Court determined that the acquisition by E.C. Knight Co. of a significant portion of sugar manufacturing did not constitute an unlawful restraint of trade under the Sherman Act because the manufacturing of sugar itself was not considered interstate commerce; rather, it was classified as a local activity.

This decision underscored the limitations of federal regulation in industries that were primarily local in nature, even if the economic impact was considerable. As a consequence, the ruling set a precedent that would affect how future antitrust cases were evaluated, particularly regarding the delineation between manufacturing and commerce. The court maintained that the regulation of manufacturing, which was seen as a local activity, fell outside the scope of Congress's authority under the commerce clause, limiting the federal government's ability to intervene in monopolistic practices in such contexts.