As a government remedy in the United States, affirmative action has been the subject of numerous legal challenges that have determined where and how it is applied. The hiring practices of federal contractors, including public universities, are subject to affirmative action. Few U.S. states require private colleges to use affirmative action in admissions; most of its application in private schools and privately owned businesses is voluntary. Several states don’t allow racial preferences in government contracting and admissions processes for public universities.