(CNN)Here is some background information about affirmative action as well as a few notable court cases.
Supporters argue that affirmative action is necessary to ensure racial and gender diversity in education and employment. Critics state that it is unfair and causes reverse discrimination.
Racial quotas are considered unconstitutional by the U.S. Supreme Court.
A 1995 study shows that white women benefited from affirmative action more than people of color.
The state of Texas replaced its affirmative action plan with a percentage plan that guarantees the top 10% of high-school graduates a spot in any state university in Texas. California and Florida have similar programs.
Timeline (selected cases):
1954 - The U.S. Supreme Court, in Brown v. Board of Education, rules that the "separate but equal" doctrine violates the Constitution.
1961 - President John F. Kennedy creates the Council on Equal Opportunity in an Executive Order. This ensures that federal contractors hire people regardless of race, creed, color or national origin.
1964 - The Civil Rights Act renders discrimination illegal in the workplace.
1978 - In Regents of the University of California v. Bakke, a notable reverse discrimination case, the Supreme Court rules that colleges can't use racial quotas because it violates the Equal Protection Clause. However, race can be used as one factor for admission.
1995 - The University of Michigan rejects the college application of Jennifer Gratz, a top high school student in suburban Detroit who is white.
October 14, 1997 - Gratz v. Bollinger, et al., is filed in federal court in the Eastern District of Michigan. The University of Michigan is sued by white students, including Jennifer Gratz and Patrick Hamacher, who claim the undergraduate and law school affirmative action policies using race and/or gender as a factor in admissions is a violation of the Equal Protection Clause of the Fourteenth Amendment or Title VI of the Civil Rights Act of 1964.
December 3, 1997 - A similar case, Grutter v. Bollinger, is filed in federal court in the Eastern District of Michigan. Barbara Grutter, denied admission to the University of Michigan Law School, claims that other applicants, with lower test scores and grades, were given an unfair advantage due to race.
December 2000 - The judge in the Gratz v. Bollinger case rules that the University of Michigan's undergraduate admissions policy does not violate the standards set by the Supreme Court.
March 2001 - The judge in the Grutter v. Bollinger case rules the University of Michigan Law School's admissions policy is unconstitutional.
December 2001 - The Sixth Circuit Court of Appeals hears appeals in both University of Michigan cases.
May 14, 2002 - The Sixth Circuit Court of Appeals reverses the district court's decision in Grutter v. Bollinger.
April 1, 2003 - The U.S. Supreme Court hears oral arguments on the two cases. U.S. Solicitor General Theodore Olson offers arguments in support of the plaintiffs.
June 23, 2003 - The Supreme Court rules on Grutter v. Bollinger that the University of Michigan Law School may give preferential treatment to minorities during the admissions process. The law school policy is upheld by a vote of five to four.
June 23, 2003 - In Gratz v. Bollinger, the undergraduate policy in which a point system gave specific "weight" to minority applicants is overturned six to three.
December 22, 2003 - The Supreme Court rules that race can be a factor in universities' admission programs but it cannot be an overriding factor. This decision impacts the Grutter and Gratz cases.
November 7, 2006 - The Michigan electorate strikes down affirmative action by approving a proposition barring affirmative action in public education, employment, or contracting.
January 31, 2007 - After the Supreme Court sends the case back to district court, the case is dismissed. Gratz and Hamacher settle for $10,000 in administrative costs, but do not receive damages.
2008 - Abigail Noel Fisher, a white woman, sues the University of Texas. She argues that the university should not use race as a factor in admission policies that favor African-American and Hispanic applicants over whites and Asian-Americans.
July 1, 2011 - An appeals court overturns Michigan's 2006 ban on the use of race and/or gender as a factor in admissions or hiring practices.
November 15, 2012 - The U.S. Sixth Circuit Court of Appeals throws out Michigan's 2006 ban on affirmative action in college admissions and public hiring, declaring it unconstitutional.
June 24, 2013 - The Supreme Court doesn't rule on the school admission policy for the University of Texas; instead it sends it back to the lower court for further review.
October 15, 2013 - The U.S. Supreme Court hears oral arguments in a case concerning Michigan's 2006 law on affirmative action.
April 22, 2014 - In a six to two ruling, the Supreme Court upholds Michigan's ban of using racial criteria in college admissions.
July 15, 2014 - The U.S. Court of Appeals for the Fifth Circuit upholds the use of race by the University of Texas as a factor in undergraduate admissions as a way of promoting diversity on campus. The vote is two to one.
December 9, 2015 - The U.S. Supreme Court hears oral arguments in the University of Texas case regarding race as a factor in admissions policies.