Constitutional lawyer David Boies believes that the Supreme Court will rule state gay marriage bans violate the US Constitution.

Boies, along with Ted Olson, represented plaintiff couples in cases challenging restrictive marriage bans in California and Virginia. They won both those cases.

(Related: Ted Olson, Tony Perkins to debate gay marriage on Fox News.)

Appearing on Bloomberg Business' With All Due Respect to discuss Friday's Supreme Court decision to hear four challenges to similar state marriage bans, Boies said that he was confident the high court would legalize such unions in all 50 states.

(Related: Supreme Court agrees to hear four cases challenging gay marriage bans.)

“The argument is overwhelming that there's a federal constitutional right to marry the person that you love and 36 states have held that. Seventy percent of people now live in a state that has constitutional or statutory marriage equality. And the history of the Supreme Court is a history of case after case after case holding that marriage is a fundamental right, that it protects individual freedom, freedom of expression, freedom of association, that it's a basic element of liberty. And I think that the Supreme Court stepped right up to that in the Windsor case.”

Boies explained that in the short term there are no consequences if the Supreme Court rules against plaintiff couples, but such a ruling would allow opponents to return to the ballot box.

“And now the courts would not presumably hold it unconstitutional under the federal constitution. You might still challenge it under the state constitutions and you may still establish it by legislation but you would not have a federal constitutional challenge if the Supreme Court goes all the way against us,” Boies.

“I don't think that's going to happen,” he added, predicting a 5-4 – or possibly 6-3 – vote in favor of plaintiffs at the Supreme Court.

“I think it's inevitable, it's the right thing to do, and we're going to have it this year,” he said.