Smith-Connally Anti-Strike Act, (June 25, 1943), measure enacted by the U.S. Congress, over President Franklin D. Roosevelt’s veto, giving the president power to seize and operate privately owned war plants when an actual or threatened strike or lockout interfered with war production. Subsequent strikes in such plants seized by the government were prohibited. In addition, war-industry unions failing to give 30 days’ notice of intent to strike were held liable for damages.