agreement between an employer and an employee in which the employee agrees, as a condition of employment, not to join a union during the course of his employment. Such contracts, used most widely in the United States in the 1920s, enabled employers to take legal action against union organizers for encouraging workers to break these contracts. A federal law prohibiting the use of yellow-dog contracts on the railroads (Erdman Act of 1898) was struck down by the Supreme Court as an unconstitutional infringement upon the freedom of contract (Adair v. The United States, 1908). In 1932, in accordance with the new philosophy that the government should not interfere with workers' right to organize, the Norris-LaGuardia Act (Norris–La Guardia Act) made yellow-dog contracts unenforceable in the federal courts.