The US Supreme Court on Tuesday upheld a constitutional amendment in Michigan banning the use of race-based preferences in the admissions decisions of public universities.

Voting 6 to 2, the high court said Michigan’s Proposal 2 did not violate the US Constitution’s Equal Protection Clause as charged by various groups favoring the use of affirmative action in college admissions.

The groups had challenged the affirmative action ban on grounds that it tilted the political playing field in Michigan in a way that made it significantly more difficult for racial minorities to enact the type of race-based college admissions policies that they favor.

A federal judge rejected the argument, but the full Sixth Circuit Court of Appeals embraced it by a vote of 8 to 7, striking down the Michigan ban.

In reversing that decision, the high court said the appeals court judges were wrong to “disempower” the 58 percent of Michigan voters who supported the constitutional amendment.

“There is no authority in the Constitution of the United States or in this Court’s precedents for the Judiciary to set aside Michigan laws that commit this policy determination to the voters,” Justice Anthony Kennedy wrote in the court’s main opinion.

“This case is not about how the debate about racial preferences should be resolved. It is about who may resolve it,” Justice Kennedy wrote in an 18-page opinion.

He added: “It is demeaning to the democratic process to presume that the voters are not capable of deciding an issue of this sensitivity on decent and rational grounds.”

Justice Sonia Sotomayor filed a 58-page dissent in which she lectured and belittled the majority justices as being “out of touch with reality.”

“My colleagues are of the view that we should leave race out of the picture entirely and let the voters sort it out,” she said.

“In my colleagues’ view, examining the racial impact of legislation only perpetuates racial discrimination,” she said in a dissent joined by Justice Ruth Bader Ginsburg.

“This refusal to accept the stark reality that race matters is regrettable,” Justice Sotomayor said.

“The Constitution does not protect minorities from political defeat. But neither does it give the majority free rein to erect selective barriers against racial minorities,” she said.

Sotomayor said the judiciary has a special role to play to safeguard minority rights that might be diminished or extinguished by majoritarian power.

“The Court abdicates that role, permitting the majority to use its numerical advantage to change the rules mid-contest and forever stack the deck against racial minorities in Michigan,” she said.

At the center of the case was the so-called political process doctrine, which holds that measures that make it considerably harder for a minority group to participate in the democratic process must be subjected to strict examination by the courts.

Although two of the majority justices, Antonin Scalia and Clarence Thomas, would have overturned the underlying legal precedents supporting the doctrine, the court’s main opinion does not do so.

Instead, Kennedy defended the democratic process. He said a holding invalidating Michigan’s constitutional amendment would have been “an unprecedented restriction on the exercise of a fundamental right held not just by one but by all in common.”

“It is the right to speak and debate and learn and then, as a matter of political will, act through a lawful electoral process,” Kennedy said.

He said such precepts do not diminish the judiciary’s role to protect racial minorities from discriminatory laws or enactments. But the Michigan constitutional amendment did not amount to such discrimination, he said.

The case stems from the controversy surrounding the Supreme Court’s 2003 decision upholding the limited use of race in admissions at the University of Michigan Law School.

Three years after that 5-to-4 decision, opponents of affirmative action placed a statewide initiative on the Michigan ballot. The measure, Proposal 2, sought to amend the state constitution to prohibit public universities, colleges, and school districts from discriminating or granting preferential treatment based on race, sex, color, ethnicity, or national origin.

Proposal 2 was adopted 58 to 42 percent.

Supporters of affirmative action filed suit to have the amendment declared unconstitutional. The litigants were led by a group called the Coalition to Defend Affirmative Action, Integration, and Immigrant Rights and Fight for Equality by Any Means Necessary.

Their lawyers argued that Proposal 2 would undercut minority enrollment at public universities in Michigan and make it much more difficult for minority students and other groups to change the policy to an approach more supportive of affirmative action.

Prior to Proposal 2, affirmative action programs were the responsibility of elected trustees at each school. Anyone who wanted to change the system could try to lobby the board members for a change.

Instead of lobbying, affirmative action opponents took the issue directly to Michigan voters in the statewide referendum to amend the state constitution.

With passage of the measure, it became significantly harder for minority students and groups to exert political influence on an equal basis with opponents of affirmative action.

Affirmative action supporters said this was a violation of the Constitution’s Equal Protection Clause and was a form of discrimination.

In essence, the charge was that a constitutional amendment that barred discrimination or preferential treatment based on race, sex, color, ethnicity, or national origin was, itself, a form of discrimination.

In an opinion concurring in Kennedy’s decision, Justice Scalia said the Michigan case existed in a “jurisprudential twilight zone.”

“We confront a frighteningly bizarre question: Does the Equal Protection Clause ... forbid what its text plainly requires?” he wrote.

“In my view, any law expressly requiring state actors to afford all persons equal protection of the laws ... does not – cannot – deny to any person equal protection of the laws,” Scalia said.

He quoted Justice Harlan’s famous statement in the 1896 decision Plessy v. Ferguson that the Constitution is colorblind. “The people of Michigan wish the same for their governing charter,” he said. “It would be shameful for us to stand in their way.”

In her dissent, Sotomayor presented an entirely different perspective.

“This case is not, as the plurality imagines, about ‘who may resolve’ the debate over the use of race in higher education admissions,” she wrote. “Rather, this case is about how the debate over the use of race-sensitive admissions policies may be resolved.”

“While the Constitution does not guarantee minority groups victory in the political process, it does guarantee them meaningful and equal access to that process,” she said.

“It guarantees that the majority may not win by stacking the political process against minority groups permanently, forcing the minority alone to surmount unique obstacles in pursuit of its goals – here, educational diversity that cannot reasonably be accomplished through race-neutral measures,” she said.

Prior to the Michigan ban, Sotomayor noted, minority enrollment at the University of Michigan stood at 12.15 percent. After the ban, by 2012, minority enrollment had dropped roughly 25 percent to 9.54 percent of the student population.

Joining Justices Kennedy, Scalia, and Thomas in the majority were Justices Samuel Alito and Stephen Breyer and Chief Justice John Roberts.

Justice Elena Kagan did not participate in the case, presumably because she worked on the issue while serving as solicitor general prior to joining the high court.

The case is Schuette v. Coalition to Defend Affirmative Action (12-682).