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

...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....

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. At the time it considered the issue in 1918, there was nothing in the Supreme Court’s case law that suggested any limit on Congress’s authority over what crossed state lines. On the contrary, the Court had upheld bans on interstate transportation of lottery tickets, contaminated food and drugs, prostitutes, and alcoholic beverages....