Bonauto, who has been the civil rights project director of Gay and Lesbian Advocates and Defenders (GLAD) for nearly 25 years, will be joined by the organization's legal director, Gary Buseck, among others.
She's the latest addition to the continually growing team of lawyers preparing to make the case against Utah's same-sex marriage ban before the Supreme Court.
And, attorney Peggy Tomsic said Tuesday, it may be the most historically significant.
"Mary Bonauto is a legend in this movement," Tomsic told The Salt Lake Tribune. "She was there at the beginning of the fight for marriage equality in Massachusetts, and she's been instrumental in the major cases that have been brought since then. For me, she brings the historical experience and wisdom of where we started and how we got here in a very deep and fundamental way."
Tomsic and her firm, Magleby & Greenwood, have led the charge against Amendment 3 since the lawsuit challenging Utah's voter-approved ban on same-sex marriage was filed last year.
After the couples' historic victory at the U.S. District Court, the National Center for Lesbian Rights (NCLR) joined their team to take the case to the 10th Circuit Court of Appeals.
Last month, former Acting Solicitor General Neal Katyal and his firm of Hogan Lovells also came aboard.
"Now that it looks like the case may be heard by the U.S. Supreme Court, we want to put together the strongest possible legal team to reflect the importance of this case," said Shannon Minter, NCLR's legal director. "It's pretty fitting that as we take this to the Supreme Court, to where this question could finally be settled for the whole country, we have our Utah counsel, we have counsel from the East and West coast and we have D.C. counsel. There's a nice aspect to that. "
Earlier this month, Utah filed its petition for certiorari with the U.S. Supreme Court, asking the justices to take Utah's case and settle the question of "whether the United States Constitution compels states to adopt a single marriage policy that every individual is allowed 'to marry the person of their choice.' "
Regardless of whether or not the U.S. Supreme Court chooses Utah's case couples from Virginia and Oklahoma have also petitioned for the high court to hear their cases the lawyers said it will only help to have as many qualified and experienced gay rights attorneys involved.
During the case that overturned significant aspects of the federal Defense of Marriage Act, extending federal benefits to same-sex spouses, Bonauto and GLAD solicited supportive "friend of the court" briefs on behalf of plaintiff Edie Windsor.
Should the high court take on another case, Buseck said, GLAD would likely lead a similar charge. But, he added, it is his and Bonauto's belief that the justices should hear Utah's lawsuit.
"While it's not the only one, Utah's case is a good vehicle for the court to take," Buseck said. "We've reached that point where the court knows that soon, it's going to be time for them to finally answer this question. We're ready. And I'm of the belief that they're ready, too. It's just a matter of waiting for them to do it."