United Farm Workers during Cesar Chavez tenure was committed to restricting immigration. Chavez and Dolores Huerta, cofounder and president of the UFW, fought the Bracero Program that existed from 1942 to 1964. Their opposition stemmed from their belief that the program undermined U.S. workers and exploited the migrant workers. Since the Bracero Program ensured a constant supply of cheap immigrant labor for growers, immigrants could not protest any infringement of their rights, lest they be fired and replaced. Their efforts contributed to Congress ending the Bracero Program in 1964. In 1973, the UFW was one of the first labor unions to oppose proposed employer sanctions that would have prohibited hiring illegal immigrants.