WASHINGTON — In a fractured decision that revealed deep divisions over what role the judiciary should play in protecting racial and ethnic minorities, the Supreme Court on Tuesday upheld a Michigan constitutional amendment that bans affirmative action in admissions to the state’s public universities.
The 6-2 ruling effectively endorsed similar measures in seven other states, including New Hampshire. It may also encourage more states to enact measures banning the consideration of race in admissions or to develop race-neutral alternatives to ensure diversity.
States that forbid affirmative action in higher education, including Florida and California, have seen a significant drop in the enrollment of black and Hispanic students in their most selective colleges.
In five opinions spanning more than 100 pages, the justices set out starkly conflicting views. The justices in the majority, with varying degrees of vehemence, said policies affecting minorities that do not involve intentional discrimination should be decided at the ballot box rather than in the courtroom.
But Justice Sonia Sotomayor, in the most passionate and most significant dissent of her career, said the Constitution required special vigilance in light of the history of slavery, Jim Crow, and “recent examples of discriminatory changes to state voting laws.”
Her opinion, longer than the four other opinions combined, appeared to reflect her own experiences with affirmative action at Princeton and Yale Law School.
“I had been admitted to the Ivy League through a special door,” she wrote in her best-selling memoir, “My Beloved World.” For years, she wrote, “I lived the day-to-day reality of affirmative action.”
In contrast to Sotomayor’s outraged dissent, Justice Anthony Kennedy’s controlling opinion for three justices took pains to say that the decision was a modest one.
“This case is not about how the debate about racial preferences should be resolved,” he wrote, in an opinion joined by Chief Justice John Roberts and Justice Samuel A. Alito. “It is about who may resolve it. 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.”
His announcement of the decision from the bench was businesslike. Signaling deep displeasure, Sotomayor summarized her dissent from the bench — an unusual move that happens perhaps three times a term. She said that, under the initiative, minorities face a burden not encountered by other applicants. Athletes, children of alumni, and students from under-represented parts of the state, she said, remained free to try to persuade universities to give their applications special weight.
“The one and only policy a Michigan citizen may not seek through this long-established process,” she wrote, “is a race-sensitive admissions policy.”
That difference, she said, violated the Constitution’s equal protection clause.
“The Constitution does not protect racial minorities from political defeat,” she wrote. “But neither does it give the majority free rein to erect selective barriers against racial minorities.”
Justice Ruth Bader Ginsburg joined the dissent.
The court’s decision appears to have no immediate impact on universities in Massachusetts or other New England states. The decision does not go so far as to invalidate the use of race in college admissions in the vast majority of states that allow the practice, including the New England states except New Hampshire.
The New Hampshire legislature banned the use of affirmative action by public colleges and other state agencies in 2011, and the Supreme Court decision leaves that law in place.
“The ruling appears to be narrowly written and is targeted at the right of Michigan voters to say their public colleges and universities should not take race into consideration in their admissions process,” said Richard Doherty, president of the Association of Independent Colleges and Universities in Massachusetts.
In earlier cases, including one from last June challenging the admissions policies of the University of Texas, the court has said that race-conscious selection can be constitutionally permissible in states that wish to use it. In a concurrence, Justice Antonin Scalia, joined by Justice Clarence Thomas, said those decisions were wrong, and he suggested that they were in peril.
The most surprising opinion came from Justice Stephen G. Breyer, who abandoned his usual liberal allies to vote with the majority, although he did not adopt their reasoning. The Constitution, he said, permits but does not require states to use race-conscious admissions for educational diversity.
In general, he said, “the Constitution foresees the ballot box, not the courts, as the normal instrument for resolving differences and debates about the merits of these programs.”
Justice Elena Kagan recused herself, presumably because she had worked on the case as US solicitor general.Marcella Bombardieri of the Globe staff contributed to this report.