The justices said in a 6-2 ruling that Michigan voters had the right to change their state constitution in 2006 to prohibit public colleges and universities from taking account of race in admissions decisions. The justices said that a lower federal court was wrong to set aside the change as discriminatory.
The decision bolstered similar voter-approved initiatives banning affirmative action in education in California and Washington state. A few other states have adopted laws or issued executive orders to bar race-conscious admissions policies.
Justice Anthony Kennedy said voters chose to eliminate racial preferences, presumably because such a system could give rise to race-based resentment. Kennedy said nothing in the Constitution or the court's prior cases gives judges the authority to undermine the election results.
"This case is not about how the debate about racial preferences should be resolved. It is about who may resolve it," Kennedy said.
In dissent, Justice Sonia Sotomayor said the decision tramples on the rights of minorities, even though the amendment was adopted democratically.
"But without checks, democratically approved legislation can oppress minority groups," said Sotomayor, who read her dissent aloud in the courtroom Tuesday. Justice Ruth Bader Ginsburg sided with Sotomayor in dissent.
Judges "ought not sit back and wish away, rather than confront, the racial inequality that exists in our society," Sotomayor said. She is one of two justices, along with Clarence Thomas, who have acknowledged that affirmative action was a factor in their admission to Princeton University and Yale University, respectively. They both attended law school at Yale. Thomas is a staunch opponent of racial preferences.
At 58 pages, Sotomayor's dissent was longer than the combined length of the four opinions in support of the outcome.
Chief Justice John Roberts and Justices Stephen Breyer, Samuel Alito, Antonin Scalia and Thomas agreed with Kennedy.
Responding to Sotomayor, Roberts said it "does more harm than good to question the openness and candor of those on either side of the debate."
Justice Elena Kagan did not take part in the case, presumably because she worked on it at an earlier stage while serving in the Justice Department.
In 2003, the Supreme Court upheld the consideration of race among many factors in college admissions in a case from Michigan.
Three years later, affirmative action opponents persuaded Michigan voters to change the state constitution to outlaw any consideration of race.
The 6th U.S. Circuit Court of Appeals said the issue was not affirmative action, but the way in which its opponents went about trying to bar it.
In its 8-7 decision, the appeals court said the provision ran afoul of the Equal Protection Clause of the U.S. Constitution's 14th Amendment because it presents an extraordinary burden to affirmative action supporters who would have to mount their own long, expensive campaign to repeal the constitutional provision.
Black and Latino enrollment at the University of Michigan has dropped since the ban took effect. At California's top public universities, African-Americans are a smaller share of incoming freshmen, while Latino enrollment is up slightly, but far below the state's growth in the percentage of Latino high school graduates.
The case was the court's second involving affirmative action in as many years. In June, the justices ordered lower courts to take another look at the University of Texas admissions plan in a ruling that could make it harder for public colleges to justify any use of race in admissions.
The case is Schuette v. Coalition to Defend Affirmative Action, 12-682.