The White Court struck down a 1916 federal child labor law 5–4 in Hammer v. Dagenhart (1918). Roland Dagenhart’s two minor sons, Reuben and John, worked with their father at a cotton mill in North Carolina. The state of North Carolina had a child labor law prohibiting children under twelve from working, but the new federal law prohibited children up to sixteen from working. Dagenhart’s two children were between the ages of twelve and sixteen, so their employ complied with state law but violated federal law.

A bare majority of the Court reasoned that the federal law exceeded Congress’s commerce powers and invaded the rights of the state under the Tenth Amendment. “Thus, the act in a two-fold sense is repugnant to the Constitution,” wrote Justice William Rufus Day. “It not only transcends the authority delegated to Congress over commerce but also exerts a power as to purely local matter to which the federal authority does not extend.”

Four justices dissented in an opinion written by Justice Oliver Wendell Holmes, who criticized the majority for its narrow conception of Congress’s powers under the Commerce Clause and for “intrud[ing] its judgment upon questions of policy or morals.”