Champion established the rule that Congress’s power to regulate commerce includes the power to prohibit commerce. In Hammer v. Dagenhart, the Court considered whether Congress could prohibit the shipment of products manufactured by children.
Hammer divided the Court 5-4. Justice Day wrote the majority opinion. He considered why Congress enacted the child labor law. The federal law, he said, “does not regulate transportation among the States, but aims to standardize the ages at which children may be employed.” Day added that Congress can “regulate commerce.” However, the federal government cannot “control the States in their exercise of the police power over local trade.”