In the 1904 case Swift and Company v. United States, the Supreme Court ruled that federal antitrust laws could be applied to meatpackers who were manipulating prices in multiple states. The court held that although individual components of their operations may have been intrastate (within a single state), taken as a whole, they constituted interstate commerce due to their impact on trade across state lines. This was significant because it expanded the interpretation of what constitutes "interstate commerce," giving more power to federal authorities under the Commerce Clause of the Constitution. The decision also established what is known as "the stream of commerce" doctrine, which holds that if part of a transaction takes place across state lines, then all parts can be regulated by Congress.

In the dissenting opinion for Swift and Company v. United States, Justice Brewer argued that the Sherman Act was not applicable to this case as it only applied to interstate commerce in its final form, not activities within a state that might affect such commerce. He contended that if every activity affecting interstate trade could be regulated by Congress under the Commerce Clause, then there would essentially be no limit on federal power over economic matters. This would undermine states' rights and upset the balance of powers between federal and state governments established by Constitution. Furthermore, he disagreed with majority's interpretation of 'direct effect' on commerce; according to him buying cattle for slaughter did not directly impact interstate trade but rather had an indirect effect which should fall outside purview of Sherman Act.