UPDATE: King & Spalding has pulled out of the case and Paul Clement has resigned from the firm. See stories here and here.

King & Spalding is entering territory where few other corporate law firms have gone for years: litigation over same-sex marriage, on the side of the opponents.

The firm’s chief appellate lawyer, former U.S. solicitor general Paul Clement, is assuming the lead role in trying to save the federal Defense of Marriage Act, the 1996 law that prohibits federal recognition of same-sex couples, and in doing so the firm is bucking what has been a consensus among several big firms and their clients to support those partnerships. King & Spalding itself offers domestic-partnership benefits and supports gay-rights groups financially, and its recruitment materials tout a near-perfect diversity score from the Human Rights Campaign, a national lesbian, gay, bisexual and transgender (LGBT) civil rights group based in Washington.

King & Spalding’s decision to defend the law is shaping up as a test of the firm’s reputation, its client relationships and its internal dynamics. The Human Rights Campaign, for example, is promising a public-relations blitz to “shame” the Atlanta-based firm and “educate clients and potential recruits” about the marriage litigation. “The firm needs to understand that there are consequences to defending discrimination,” said Michael Cole-Schwartz, a spokesman for the group.

Separately, King & Spalding is treading carefully around another consideration that threatened the firm’s bottom line. Clement is representing the U.S. House of Representatives’ Republican leadership, and a House ethics rule limits the lobbying that a firm can do when it takes on a contract to work for the House. House members have interpreted that rule strictly in the past, in a way that would cripple a lobbying practice, but King & Spalding’s contract gives the firm greater leeway.

The firm would not be involved as lead counsel in the marriage litigation but for the Obama administration’s decision in February to abandon the Defense of Marriage Act as unconstitutional. President Barack Obama said the law was unlikely to survive heightened scrutiny, a determination that conservatives sharply criticized as caving to gay-rights groups.

Sidley Austin partner Bradford Beren­son, who served as an associate counsel to President George W. Bush, said King & Spalding does not deserve to be punished for filling the vacuum left by the U.S. Department of Justice. “In general, most people feel that lawyers should be free to take on unpopular clients or unpopular causes without fear of retribution, and most law firms would not be well served by shying away from controversy,” Berenson said. “After all, controversy is at the heart of what any litigator is involved in day-to-day.”

He and others compared King & Spalding’s decision to that of lawyers who took on the defense of terrorism suspects detained at Guantánamo Bay, Cuba.

Ty Cobb, the Human Rights Campaign’s legislative counsel, said he sees the Defense of Marriage Act cases as different. “In a situation where someone’s accused of a crime, or you have someone whose civil liberties are at stake, within the legal community we see it as a professional obligation to represent those clients. It’s a different situation there,” he said.

Several King & Spalding partners, including Clement and firm Chairman Robert Hays Jr., did not respond to interview requests last week. A firm spokesman, Les Zuke, said they would have no comment on the matter because it involves “client representation.” The House’s general counsel, Kerry Kircher, did not respond to interview requests.

So far, Clement and two other firm lawyers have filed to intervene in a case in the Southern District of New York in which an 81-year-old woman, Edith Windsor, is challenging a $363,000 estate-tax bill that she would not have owed if she had married a man; she married a woman in Canada, and the woman died in 2009. An appearance in another federal case out of Connecticut is due April 26, and the House may intervene in other cases.

BREAKING GROUND

King & Spalding’s involvement is unusual because, until now, the task of defending heterosexual marriage has typically fallen to the Justice Department or to boutique law firms often involved with politically conservative causes. In the legal fight over California’s Proposition 8, which banned same-sex marriage, corporate heavyweights Gibson, Dunn & Crutcher and Boies, Schiller & Flexner took up the side of same-sex couples. On the other side was Cooper & Kirk, a small litigation shop in Washington that’s less reliant on corporate work and is known for taking on ideologically charged cases.

Berenson said King & Spalding must have been well aware of the potential consequences of breaking from that pattern.

“The whole range of div­ersity issues is very important to the large corporate clientele of big firms, so it wouldn’t be honest or realistic to suggest that those firms don’t think about those things,” he said. “Every firm approaches it in a somewhat different way and makes a somewhat different choice.”

King & Spalding has represented several companies in the Standard & Poor’s 500 Index, including The Coca-Cola Co. and General Motors Co., both of which have nondiscrimination policies and perfect scores from the Human Rights Campaign. A GM spokesman declined to comment last week about King & Spalding’s involvement in the marriage litigation, while Coca-Cola and several other firm clients did not respond to requests for comment.

The firm’s Web site has a page devoted to promoting diversity, including the recruitment of LGBT lawyers. “We work hard to foster and maintain an environment where our lawyers can provide the highest level of legal service while being true to themselves in the process,” the site says.

But one section of the firm’s five-page contract with the House appears to limit what employees can do in the debate over gay rights. The section says all partners and employees, even those not involved in the contract, “will not engage in lobbying or advocacy for or against any legislation” that would “alter or amend in any way the Defense of Marriage Act.” Gay-rights lawyers interpret that to be a gag order for firm employees. That includes one employee, Atlanta associate Brian Basinger, who is president of the Stonewall Bar Association of Georgia, a group that pushes for gay rights.

“It does appear to me to be a bit draconian, in that it could be interpreted to limit employees of the law firm from doing LGBT work in their private time,” said Jeffery Cleghorn, the immediate past president of the Stonewall Bar Association and a name partner at Atlanta’s Kitchens New Cleghorn.

Cleghorn, speaking for himself and not the association, said King & Spalding’s decision to take on the marriage cases “really is inconsistent with how we in Atlanta, I think, have viewed King & Spalding in recent years.” He said the firm has been supportive of the gay bar and of a separate advocacy group, Georgia Equality.

The Human Rights Campaign is planning to use several tactics to pressure King & Spalding, including advertisements entitled “Shame,” letters to clients and law schools and a re-evaluation of the firm’s score of 95 on its “equality index,” which takes into account factors such as “responsible citizenship.”

In another example of a corporate firm taking a case in opposition to gay marriage, Foley & Lardner filed suit last year trying to halt such marriages in the District of Columbia. The Human Rights Campaign deducted 15 points from the firm’s score on its index because, spokesman Cole-Schwartz said, “they had taken proactive action that undermined LGBT equality.” Whether those points cost the firm any clients or law-school recruits is unclear; Foley & Lardner did not respond to interview requests last week.

LOBBYING FALLOUT AVOIDED

King & Spalding’s lobbying practice may have escaped fallout from a House ethics rule that has beguiled other firms working on contract for the House.

Under Rule 18(b) of the Code of Official Conduct, neither a contract employee nor anyone else at the employee’s firm may lobby the relevant “contracting committee.” In 2007, the rule threatened Arnold & Porter’s lobbying practice when Irvin Nathan, then a partner there, was on contract with Democrats on the House Judiciary Committee to investigate the firings of U.S. attorneys; Nathan left the firm to become the House’s general counsel. In 2009, Alan Baron jumped from Holland & Knight to Seyfarth Shaw to avoid interrupting the former’s lobbying practice while he led impeachment inquiries of two federal judges.

A version of the rule has been in place since at least 2000. It’s intended to stop a firm from profiting off the cachet that comes with working on a high-profile House contract.

The House Ethics Com­mittee has given guidance that the rule is to be followed strictly, so that a firm isn’t collecting fees from House members at the same time as its lobbying practice is trying to influence the actions of those same members. A memo from the committee dated April 12, 2000, reads in part: “During the term of the contract, other members of the firm should have no involvement with the activities of the contracting committee (including, for example, counseling or representing witnesses) and should not lobby the contracting committee (including its members, staff or others providing services to that committee).”

In this instance, King & Spalding is not working for one of the House’s standing committees. The firm’s contract is with the House general counsel, and it is representing the House’s leadership team, including Speaker John Boehner (R-Ohio). So in contrast to the other examples in recent years, the firm’s lobbyists are free to try to influencemembers, including the Republican leadership, on anything not related to the lawsuits. Even Clement could lobby as long as it’s on something, like an antitrust matter, that’s not tied to pending legislation.

King & Spalding reported $3.4 million in federal lobbying revenue in 2010, not enough to place it among the top lobbying shops in Washington. Its clients include Bacardi USA Inc., Micron Technology Inc. and Raytheon Co.

House Minority Leader Nancy Pelosi (D-Calif.) sent a letter to Boehner last week questioning what restrictions are being imposed on King & Spalding’s lobbying practice, “to ensure that no conflicts of interest arise on behalf of its extensive list of corporate clients while that firm is employed by the House.”

Boehner had not responded by late in the week.

David Ingram can be contacted at dingram@alm.com.