NEW YORK, Dec 10 (Reuters Legal) - Lawyers for women seeking to bring the largest sex-discrimination class-action lawsuit in U.S. history have settled on who will argue the case before the Supreme Court: Joseph M. Sellers, a partner at Washington D.C., plaintiffs' class-action law firm Cohen Milstein Sellers & Toll.

Sellers, 57, a veteran civil-rights litigator, has been co-lead counsel in the case, Wal-Mart Stores v. Dukes et al, since 2000. Other attorneys on the plaintiffs' side said it was clear from the start that either Sellers or lead counsel Brad Seligman, 59, would make the oral argument before the Supreme Court. Lawyers at three other plaintiffs' law firms and two other nonprofits are also representing would-be members of a class of women who claim Wal-Mart paid them less than men and offered fewer opportunities for promotions.

Arguing for Wal-Mart will be high-profile litigator Theodore J. Boutrous, Jr., 50, a partner at Gibson, Dunn & Crutcher in Los Angeles. Boutrous has been the company's lead counsel on the case since it reached the U.S. Court of Appeals for the 9th Circuit in 2004. Wal-Mart is seeking to overturn the appellate court's decision to grant class certification to the women, a group that could number as many as 1.5 million.

When many lawyers are representing one side, as is the case with the potential class here, competition for the prestigious role of arguing before the high court can be intense. But the group chose Sellers by consensus, plaintiffs' attorneys said. On Dec. 6, shortly after the Supreme Court announced it had granted certiorari, Sellers and Seligman organized an afternoon conference call with other plaintiffs' attorneys to discuss strategy. Seligman, a lawyer at the Impact Fund, a Washington, D.C.-based nonprofit, says he nominated Sellers to do the oral argument, and others on the call supported the choice.

Another lawyer involved in the discussions said that it was generally understood that it was Sellers' turn since Seligman had twice argued the case before the 9th U.S. Circuit Court of Appeals-first before a three-judge panel, then before the court en banc. The decision was finalized two days later, after Sellers and Seligman got the approval of their clients.

The Wal-Mart case, which is expected to be heard in March, would be Sellers' second oral argument before the Supreme Court. In 2000, he represented a woman who had challenged the terms of her mobile-home financing agreement. The Court in that case, Green Tree Financial Corp. v. Randolph, ruled in favor of Sellers' client on one issue and against him on another.

Sellers has represented plaintiffs in workplace discrimination suits individually and through class actions. In another sex-discrimination case against a major company, Beck v. Boeing Co., he represented a class of more than 28,000 female employees at Boeing facilities in Washington state. Boeing settled in 2004, agreeing to pay plaintiffs up to $72.5 million.

Prior to joining Cohen Milstein in 1997, Sellers was head of the Employment Discrimination Project of the Washington Lawyers' Committee for Civil Rights and Urban Affairs for more than 15 years. He graduated from Case Western Reserve School of Law. Sellers said he started preparing for the oral argument the day he was chosen. "It's certainly a high point [for me]," he said. "This case could profoundly affect the enforcement of civil rights law in this country."

Boutrous, who received his J.D. from the University of San Diego, has represented corporations and other clients in federal and state court. He represented Time Inc. and Matthew Cooper in contempt proceedings related to the Valerie Plame case, and in 2004 persuaded the Michigan Supreme Court to overturn the largest sexual harassment verdict in U.S. history against DaimlerChrysler Corp. He is one of the lead lawyers for the plaintiffs in the pending federal constitutional challenge to California's ban on same-sex marriage.

The Wal-Mart case marks Boutrous' first argument before the Supreme Court. Boutrous said he looks forward to arguing the case and called the class certification unfair. "This case presents extremely important class action issues -- not just for Wal-Mart but for all employers, large and small, and employees nationwide," he said.

The case is Wal-Mart Stores v. Dukes et al, U.S. Supreme Court, No. 10-277. In addition to Cohen Milstein Sellers & Toll and the Impact Fund, the petitioners are the San Francisco non-profit Equal Rights Advocates, the Baltimore non-profit Public Justice Center, San Francisco law firm Davis Cowell & Bowe and Santa Fe, New Mexico-based law firms Tinkler Law Firm and the Bennett Firm. In addition to Theodore Boutrous of Gibson, Dunn & Crutcher, Wal-Mart is represented by Gibson Dunn lawyers Theodore B. Olson, Rachel S. Brass, Theane Evangelis Kapur, Mark A. Perry and Amir C. Tayrani.

(Reporting by Moira Herbst of Reuters Legal; Research assistance by Terry Baynes of Reuters Legal)