The California case on Proposition 8 could be far more significant because it involves the right to marry. Ted Olson and David Boies, the attorneys who led the challenge, plan to argue broadly that marriage is a fundamental right and that excluding gay couples from marriage denies them the equal protection of the law.

A Kennedy-Scalia clash from a decade ago gives a preview. When two gay men challenged a Texas anti-sodomy law, Kennedy wrote a glowing opinion taking their side. “They are entitled to respect for their private lives,” he said, and “the state cannot demean” them by treating them as second-class citizens.

In a moment of high drama, Kennedy gave a professorial reading of his opinion on the last day of the court term in 2003. When he finished, Scalia’s voice cut through the room as he delivered an angry dissent.

Kennedy’s opinion left the laws against same-sex marriage “on pretty shaky grounds,” Scalia said at the time. “If moral disapprobation of homosexual conduct is ‘no legitimate state interest’ … what justification could there possibly be for denying the benefits of marriage to homosexual couples?”