He gained a reputation as a fiery and devoted reformer. La Guardia sponsored labor legislation and railed against immigration quotas. His major legislation was the Norris–La Guardia Act, cosponsored with Nebraska senator George Norris in 1932. It circumvented Supreme Court limitations on the activities of labor unions, especially as those limitations were imposed between the enactment of the Clayton Antitrust Act in 1914 and the end of the 1920s. Based on the theory that the lower courts are creations not of the Constitution but of Congress, and that Congress therefore has wide power in defining and restricting their jurisdiction, the act forbids issuance of injunctions to sustain anti-union contracts of employment, to prevent ceasing or refusing to perform any work or remain in any relation of employment, or to restrain acts generally constituting component parts of strikes, boycotts, and picketing. It also said courts could no longer enforce yellow-dog contracts, which are labor contracts prohibiting a worker from joining a union.