Boyce F. Martin Jr., a defiantly liberal federal appellate judge whose rulings in two seminal cases — on favoring minority applicants in college admissions and on upholding President Obama’s requirement that Americans buy health insurance — were upheld by the Supreme Court, died on June 1 at his home in Louisville, Ky. He was 80.

The cause was brain cancer, his son Boyce R. Martin III said.

In 2002, Judge Martin wrote for the majority in a bitterly divided United States Court of Appeals for the Sixth Circuit in Grutter v. Bollinger, the affirmative action case involving the University of Michigan Law School. (The court sits in Cincinnati and covers Kentucky, Ohio, Michigan and Tennessee.)

He ruled that higher education recruiters could seek a “critical mass” of black and Hispanic students to achieve racial, ethnic and intellectual diversity among their newcomers. The decision was affirmed by the United States Supreme Court, 5 to 4, in 2003, with Justice Sandra Day O’Connor writing the majority opinion.

Lee C. Bollinger, a former dean of the law school and then the incoming president of Columbia University, warned at the time that “a ruling that race and ethnicity could not constitutionally be considered in admissions would be drastic and disheartening, threatening a decline in minority enrollment of as much as 70 to 75 percent.”