The Supreme Court has ruled that a Michigan ballot initiative to ban racial preferences in college admissions is constitutional, overturning a lower court decision.

In a 6-2 decision Tuesday, the justices said the 6th Circuit Court of Appeals was wrong to set aside the voter-approved ban as discriminatory.

Justice Anthony Kennedy announced the decision and wrote an opinion in the case Schuette v. Coalition to Defend Affirmative Action, while Chief Justice John Roberts, Justice Antonin Scalia and Justice Stephen Breyer authored concurring opinions. Justices Sonia Sotomayor and Ruth Bader Ginsburg dissented, and Justice Elena Kagan recused herself from the case.

Kennedy stressed that the case was not about the constitutionality or merits of the race-conscious admissions policies of colleges and universities, but instead hinged on whether voters in the state may choose to prohibit consideration of such preferences.

"Here, the principle that the consideration of race in admissions is permissible when certain conditions are met is not being challenged," Kennedy wrote in the majority opinion.

He said nothing in the Constitution or the court's prior cases allowed judges to undermine the will of voters.

"The decision by Michigan voters reflects the ongoing national dialogue about such practices," Kennedy wrote.

The Michigan ballot initiative, known as Proposal 2, was passed in 2006. The 6th Circuit overturned Proposal 2 in 2012. (Update at 11:50 a.m. ET: The San Jose Mercury News says the case has "major implications" for a similar ban, known as Proposition 209, that was passed by California voters in 1996.)

Sotomayor, who read her dissent from the bench, noted that "without checks, democratically approved legislation can oppress minority groups.

"For that reason, our Constitution places limits on what a majority of the people may do," she said. "This case implicates one such limit: the guarantee of equal protection of the laws."

The American Civil Liberties Union, NAACP Legal Defense Fund and others had challenged Proposal 2, saying it unfairly and unconstitutionally rigs the admissions system against minority students.

"Minority students and others who support a broadly diverse student body should not have to overturn a constitutional amendment simply to have their voices heard in the admissions process when everyone else can go directly to the university," the ACLU said in a fact sheet about the case.

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