In United States v. Carolene Products Co. (1938), the Supreme Court formulated the rational basis test. The federal statute at issue was the Filled Milk Act of 1923, which prohibited interstate commerce involving the sale of filled milk. The defendant challenged the law on Commerce Clause and Due Process grounds. In upholding the statute, the Supreme Court concluded that the law was “presumptively Constitutional”; and because the legislature had a rational basis for believing that its law was in pursuit of some legitimate government purpose, the Court declined to step in and overrule the statue.
In Footnote Four of the decision written by Justice Harlan Stone, the Court suggested several levels of judicial review: “There may be a narrower scope for operation of the presumption of constitutionality when legislation appears on its face to be within a specific prohibition of the Constitution, such as those of the first ten amendments, which are deemed equally specific when held to be embraced within the Fourteenth…. It is unnecessary to consider now whether legislation which restricts these political processes such as voting, expression, and political association which can ordinarily be expected to bring about repeal of undesirable legislation, is to be subjected to more exacting judicial scrutiny under the prohibitions of the Fourteenth Amendment than are most other types of legislation….”