What constitutional provision did the Supreme Court use to strike down the Bakeshop Act's hours provision?

In Lochner v. New York (1905), the U.S. Supreme Court struck down the hours provision of the Bakeshop Act by invoking the due process clause of the Fourteenth Amendment.1

The Court held that the law constituted an unconstitutional infringement on the freedom of contract, which it determined was a protected aspect of the "liberty" guaranteed by the Fourteenth Amendment's due process clause. The majority argued that because baking was not a dangerous or unhealthful trade, the state could not justify the law as a valid exercise of its police power to protect public health.1