Blue Cross Blue Shield of Michigan can't become a for-profit company under a state law passed in 1980. That was the legal opinion released Tuesday by Attorney General Jennifer Granholm.
Blue Cross is a nonprofit company that provides health insurance to nearly five million Michigan residents.
Granholm opinion comes as lawmakers continue to debate the status of Blue Cross.
Republican lawmakers introduced bills in May that would reduce the size of Blue Cross's board and require lawmakers approve its sale or conversion to a for-profit company.
Those bills have not passed the House.