CHICAGO (Reuters) - A federal appeals court on Friday struck down a Michigan law that banned affirmative action in college admissions, creating the possibility of a Supreme Court battle.

The 6th U.S. Circuit of Appeals, in a 2-1 decision, found that Proposal 2, a 2006 amendment to the Michigan constitution, "unconstitutionally alters Michigan's political structure by impermissibly burdening racial minorities."

The Michigan Attorney General's office was not immediately available for comment. It is possible the office could ask the entire 6th Circuit to review the case.

Appellate Court Judge R. Guy Cole wrote in the majority decision that the U.S. Supreme Court has twice held that the equal protection clause in the U.S. Constitution does not permit the kind of political restructuring caused by the Michigan law.

In her dissent, Appellate Judge Julia Smith Gibbons wrote that Proposal 2 does not draw distinctions on the basis of race but "in fact, it prohibits them."

The fight over affirmative action policies at Michigan's public colleges and universities began in the 1960s and 1970s, when African-American and other minority students first successfully lobbied for the policies' adoption.

The U.S. Supreme Court held in 2003 that universities cannot establish quotas for members of certain racial groups, but may consider race or ethnicity as a "plus" factor along with other factors.

Proposal 2 banned sex and race-based preferences in public education, public employment and public contracting.

(Writing by Mary Wisniewski, Editing by Jerry Norton)