The two attorneys who argued for the repeal of Proposition 8 in front of the Supreme Court last June -- Theodore B. Olson and David Boies -- opened up this week's Civil Rights Summit in Austin with a discussion about gay rights as a civil rights issue.

Larry Pascua celebrated the Supreme Court's rulings on Proposition 8 and the Defense of Marriage Act in San Francisco last June.  (AP Photo/Mathew Sumner)

Daily Beast editor John Avlon moderated the conversation, introducing the pair as a "legal odd couple." The "star legal duo" first worked the Supreme Court in Bush v. Gore, where they faced off from opposite sides. However, both Olson, a conservative, and Boies, definitely not a conservative, believe that there is no legal argument to support denying LGBT couples the right to marry.

"Part of being good lawyer is guessing arguments of the other side," Boies said. "I'm usually pretty good at that. The other side doesn't have any good arguments. They have a bumper sticker that says marriage is between a man and a woman."

His statement is backed up by the legal reasoning of the more than 30 federal judges who have considered this issue since California's Proposition 8 -- which banned same-sex marriage in that state -- was struck down last June.

"Every single one of them," Boies said, "all ruled the same way. All ruled that marriage is a constitutional right. That's extraordinary."

The two also discussed how quickly public opinion has shifted on the matter. In the late 1960s, only a few years after the Civil Rights Act of 1964 was signed by President Lyndon B. Johnson -- whose library hosted the event where Olson and Boies were speaking -- a group petitioned the Civil Rights Commission to regulate existing rules that prohibited openly gay people from working for the government. The petition was denied. Up until Lawrence v. Texas in 2003, it was illegal to engage in "homosexual behavior" in Texas.

When Olson and Boies began working on the Prop. 8 case in March 2009, a majority of the country opposed same-sex marriage -- by a margin of 17 percent. When they won the case in June, a majority of the public approved of same-sex marriage, shifting upward by a margin of 25 percent. Now, five years later, about 10 percent or 11 percent more of the public supports same-sex marriage than opposes it.

Olson and Boies are targeting Virginia as their next fight for expanding same-sex marriage rights. Not only does Virginia's constitutional ban have some of the strongest-worded limitations on same-sex marriage, the state also provides an important symbolic background because of the 1967 case on interracial marriage, Loving v. Virginia. As Olson reminded the audience, President Obama's parents would have been guilty of a felony if they had tried to move to Virginia and get married before the landmark Supreme Court case.

Olson, who has lived in the state since the 1980s, listed the names of the founding fathers who had lived in Virginia. Boies said he and Olson wanted to "implement the principles the founding fathers articulated in Virginia."  They will argue the case Bostic v. Schaefer at the Fourth Circuit Court of Appeals in Richmond on May 13.

They have also expressed interest in working on cases involving same-sex marriage bans in Utah and Oklahoma.

An HBO documentary on the Prop 8 case, "The Case Against 8," comes out in June, and the pair's book on their experience with the case, "Redeeming the Dream," will be out later this year. Both lawyers said they were excited for the world to finally meet the plaintiffs through the film and book. Boies said he regrets that the Supreme Court decided not to allow the case to be televised because you could not listen to the plaintiffs on the stand "and not be moved. They were our best evidence."

As for the future of same-sex marriage, Boies said he was quite sure this would be a settled issue in 10 years, given that people under age 30 show broad support for gay rights and that state legislatures are coming onboard. But he conceded that this issue was far from being won across the globe. He compared the current battle over gay rights to the civil rights era of the mid-20th century. When President Harry Truman desegregated the armed forces and the Supreme Court ruled on Brown v. Board of Education, Congress was not on the same page. It took a decade before lawmakers passed the Civil Rights Act.

"I'm quite hopeful that we'll see bipartisan cooperation on this issue as we move forward," Boies said, citing the work of Republicans Paul Singer, Ken Mehlman and Olson -- and the minds Olson and Boies had already changed, such as conservative David Blankenhorn. "It's extremely important that we present this not as a left or right issue ... but as a constitutional civil rights issue," he said as the audience applauded.

Boies and Olson also explained their legal reasoning for supporting same-sex marriage. Olson spoke of the conservative values inherent in expanding marriage, while Boies cited the discrimination involved in denying equal rights to a subsection of the population. Both said that, at heart, same-sex marriage is about the 14th Amendment, just like the Civil Rights Act was: Equal protection under the law and due process mean that you can't deny gay couples from having relationships open to the rest of the public. They also added the First Amendment to the mix, which forbids people from imposing their protected religious beliefs on others.

"We don't want to jam this issue down people's throat" Boies said. "We just want them to understand what this country is all about."

Everyone in the United States has discriminated against someone, Boies said, "especially anyone as old as Ted and I are."

He added: "We need redemption, and everyone else does, too."