Andrew Koppelman is professor of law and political science at Northwestern University.

It took decades for Congress to address the problem. When, at long last, federal legislation was passed, some people raised constitutional objections, but few took them seriously. The objections required the Supreme Court to adopt unheard-of constitutional theories, hamstringing well-established powers on the basis of hysterical fears about a tyrannical federal government. Even the law’s opponents were surprised when the Court took those objections very seriously. Some warned that the Court was overreaching, and that its intervention would seriously hurt large numbers of innocent people, but the Court thought it was more important to rein in Congress.

You might assume I’m talking about health care reform. I’m not. I’m talking about child labor—and a 1918 decision by the Supreme Court that history has not looked kindly upon.

The parallels between the child labor issue and the health care issue are remarkable. In both cases, the legislation in question was the product of a decades-long struggle. Universal health care has famously been a goal of American liberals since Theodore Roosevelt proposed it in 1912. The movement to abolish child labor, for its part, stretches back to the first years after the Civil War: When the Knights of Labor was founded in 1869, its constitution included a provision calling for abolition of child labor, and a similar position was adopted by the American Federation of Labor when it was created in 1886. The National Child Labor Committee was organized in 1904, and the first federal law was introduced in 1906. For his part, Roosevelt supported a national study of the problem.

Only the federal government could address the issue, since no state would act on its own. Even states that did not want child labor could not afford to get rid of it if their competitors still had it. Health care presents a similar problem: Any state that provides good medical care risks attracting sick people from other states. In both cases, unless Congress took action, the problem was going to stay unsolved. And so in 1916, Congress, using its power to regulate interstate commerce, banned the interstate shipment of the products of child labor. When it defended the law in Court, the government explained that this was an interstate problem: "The shipment of child-made goods outside of one State directly induces similar employment of children in competing states."

Both then and now, challengers to the statutes had to propose that the Supreme Court invent new constitutional rules in order to strike them down...