The Filled Milk Prohibition

In 1923, Congress decided that a very specific culinary imposter needed to be stopped. They passed the Filled Milk Act, banning the interstate shipment of skimmed milk blended with any fat or oil other than pure milk fat. It was a targeted strike against products like 'Milnut,' an inexpensive concoction made of skimmed milk and coconut oil.

When the Carolene Products Company was indicted for shipping Milnut across state lines, they did not go quietly. They challenged the law in court, arguing that it violated the Fifth Amendment by interfering unreasonably with their right to do business. Under standard economic logic at the time, telling a company it cannot sell a harmless, clearly labeled food product because it threatens dairy farmers looks like a clear overreach.

But the Supreme Court took a different view. They upheld the Filled Milk Act, establishing a sweeping new rule: economic regulations were now 'presumptively constitutional' under a deferential 'rational basis' test. If the legislature could imagine any conceivable justification for a law, the courts would not second-guess it. Economic liberty took a backseat, leaving businesses largely at the mercy of legislative whims.

Tucked away inside this defeat for the humble coconut-oil blend, however, was a stray observation that changed American law forever. In what history remembers simply as 'Footnote Four,' the Court suggested that while economic regulations deserved a free pass, a more rigorous standard of review might be necessary for laws affecting 'discrete and insular minorities' or constitutional rights.

It is a strange irony of legal history. A routine piece of protectionist dairy legislation, designed to crush a cheap substitute for cream, accidentally birthed the modern framework for protecting civil rights and constitutional liberties.