Now, the high court is weighing whether that change to Michigan's constitution is itself discriminatory.
It is a proposition that even the lawyer for civil rights groups in favor of affirmative action acknowledges a tough sell, at first glance.
"How can a provision that is designed to end discrimination in fact discriminate?" said Mark Rosenbaum of the American Civil Liberties Union. Yet that is the difficult argument Rosenbaum will make on Tuesday to a court that has grown more skeptical about taking race into account in education since its Michigan decision in 2003.
A victory for Rosenbaum's side would imperil similar voter-approved initiatives that banned 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.
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 is 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.
For Michigan Attorney General Bill Schuette, whose office is defending the measure known as Proposal 2, the case is simple.
"We are saying no preferences. We're not discriminating. We're saying equal treatment," Schuette said.
But the federal appeals court in Cincinnati that ruled on the dispute concluded that the matter was not that straightforward.
The issue, according to the 6th U.S. Circuit Court of Appeals, was not affirmative action, but the way in which its opponents went about trying to bar it.
That is why the ACLU's Rosenbaum said, "This is a case about means, not about ends. It is not about whether a state can choose not to have" affirmative action.
In its 8-7 decision, the appeals court said the provision runs 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.
That burden "undermines the Equal Protection Clause's guarantee that all citizens ought to have equal access to the tools of political change," Judge R. Guy Cole Jr. wrote for the majority on the appeals court.
The governing boards at the University of Michigan, Michigan State University and other public colleges set admissions policies at the schools, which included the use of affirmative action before the amendment passed.
Other groups seeking changes in admissions still could lobby the policymakers at the schools. Only proponents of affirmative action would have to change the constitution, the appeals court said.
The appeals court vote broke along party lines, and there were other oddities. Two Republican-appointed judges sat out the case because of their ties to Michigan schools. One judge in the majority, Martha Craig Daughtrey, is a senior judge and typically would not be allowed to take part in the full appeals court hearing. But she sat on the original three-judge panel that heard the case.
Civil rights and education experts who are not involved in the case at the high court said they expect the justices to overturn the 6th Circuit ruling.
Harvard University Law School professor Tomiko Brown-Nagin said five of the Supreme Court justices "are skeptical of race-conscious affirmative action" and could be expected to side with Michigan. Those justices are Chief Justice John Roberts, Samuel Alito, Anthony Kennedy, Antonin Scalia and Clarence Thomas.
But Brown-Nagin said impact of such a ruling would be muted because "affirmative action already is on life support."
Peter Kirsanow, a Republican member of the U.S. Commission on Civil Rights and an opponent of racial preferences, was more blunt. "I would eat a copy of the 14th Amendment if in fact the court upholds the 6th Circuit's decision," Kirsanow said.
Justice Elena Kagan will not take part in the Michigan case, just as she excused herself from last term's case about the University of Texas admissions program. Kagan worked on the cases while serving in the Justice Department before she joined the court.
The case is Schuette v. Coalition to Defend Affirmative Action, 12-682.
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