David Boies, one half of the legal team challenging the constitutionality of California's gay marriage ban, Proposition 8, says U.S. Supreme Court Justice Antonin Scalia could vote against it.

Boies made his comments on MSNBC's Hardball with Chris Matthews.

Boies and Ted Olson argued against the ban during a 13-day trial presided by U.S. District Judge Vaughn R. Walker in January. Walker declared Proposition 8 unconstitutional in August.

The legal team returned to court on Monday, arguing in the appeal of the case before the Ninth U.S. Circuit Court of Appeals in San Francisco. The three-judge panel hinted they'll support a narrow ruling against the gay marriage ban.

On the program, Boies was definitely feeling confident, telling Matthews that if the case moved up the next legal rung, Scalia, the Supreme Court's most conservative justice, could vote against the ban.

“We've always believed from the beginning this was not a conservative or liberal, Republican or Democratic issue. This was an issue of constitutional rights,” Boies said. “And conservatives, at least as much as liberals, want to keep the government out of people's private lives. So, I think that this is something that we could win – no one ever likes to predict you're going to win 9-0 – but we could win every justice on this.” (The video is embedded in the right panel of this page.)