(Susan Walsh/AP)

Supporters of affirmative action faced an uphill battle Tuesday in convincing the Supreme Court that a Michigan constitutional amendment banning the use of racial preferences in university admissions should be thrown out.

An appeals court had said that the amendment, approved by 58 percent of the state’s voters in 2006, had restructured the political process in a way that unfairly targeted minorities.

But Michigan Solicitor General John J. Bursch told the justices Tuesday it was illogical that the amendment could offend the U.S. Constitution’s protection against discrimination, because the state was simply requiring a color-blind selection process. By contrast, Bursch said, the previous times the Supreme Court has disallowed “political restructuring” were when the government or voters had acted against proposals designed to prevent discrimination.

The Michigan amendment, he said, takes race out of the process. At issue at the Supreme Court is language that says state colleges and universities “shall not discriminate against, or grant preferential treatment to, any individual or group on the basis of race, sex, color, ethnicity, or national origin.”

Bursch said it is a “broad-based law that was primarily motivated by the people of Michigan’s decision to move past the day when we are always focused on race.”

The amendment was approved by voters after the Supreme Court, in another case from Michigan, in 2003 allowed the limited use of race as part of an “individualized, holistic review of each applicant’s file.”

Bursch received his toughest questioning from Justice Sonia Sotomayor, who has said affirmative action helped lift her out of a poor Hispanic neighborhood in the Bronx and allowed her entry into Princeton University and Yale Law School.

Sotomayor said the Michigan constitutional amendment was an attempt to disallow the use of what the Supreme Court had found to be “the one remedy that might work” in bringing diversity to the state’s universities, including the highly selective University of Michigan.

But upholding the appeals court’s decision would require the high court’s liberals to sway at least one of the five conservatives, who have shown they are highly skeptical of racial remedies.

Chief Justice John G. Roberts Jr. disputed the argument of Mark D. Rosenbaum, an American Civil Liberties Union lawyer representing one set of challengers, that the decision of Michigan voters deserved special scrutiny.

“Is it unreasonable for the state to say, ‘Look, race is a lightning rod. . . . We want to take race off the table and try to achieve diversity without racial preferences’?” Roberts asked.

When lawyer Shanta Driver, representing the Coalition to Defend Affirmative Action, said the equal-protection clause of the U.S. Constitution was meant to protect minorities’ rights from attack by a powerful “white majority,” Justice Antonin Scalia asked her to name “any case of ours” in which the court reached such a holding.

“We’ve held that the 14th Amendment protects all races,” Scalia said. “I mean, that was the argument in the early years, that it protected only the blacks. But I thought we rejected that.”

But Justice Ruth Bader Ginsburg said the equal-protection clause was a protection for minorities. “And so the view then was we use strict scrutiny when the majority is disadvantaging the minority,” she said.

The majority agreed that the Supreme Court’s action in the first Michigan case — Grutter v. Bollinger — did not require the use of racial considerations.

But the U.S. Court of Appeals for the 6th Circuit, which narrowly tossed out the Michigan amendment, ruled there is a difference between not using affirmative action and banning it in the state constitution. The latter violates the principle that minorities must be allowed to fully participate in creating laws and that “the majority may not manipulate the channels of change so as to place unique burdens on issues of importance to them,” Judge R. Guy Cole Jr. wrote.

His comparison was that while residents of Michigan’s Upper Peninsula may lobby decision makers to grant preferences to their underrepresented students, minority groups would now have to change the constitution before even having a chance to advocate racial considerations because of the amendment.

The case is Schuette v. Coalition to Defend Affirmative Action. Only eight justices will decide the case, because Justice Elena Kagan recused herself. As is customary, she gave no reason, but she probably worked on the issue while serving as the Obama administration’s solicitor general.

Last term, in a case challenging the University of Texas’s use of race in making some admission decisions, the court declined to revise its holding in Grutter. The justices sent the case back to a lower court for a closer look at whether the university had used all the tools at its disposal to increase racial diversity before resorting to the use of race.