A retired federal judge who recently ruled in favor of California's largest agricultural water agency is now an attorney for that agency in a different lawsuit.

Judge Oliver Wanger, who retired Sept. 30 from the federal district court in Fresno, recently was named in a court filing as an attorney for Westlands Water District. The district delivers water to farms in the San Joaquin Valley, most of it diverted from the Sacramento-San Joaquin Delta.

Just weeks before retirement, Wanger ruled in favor of Westlands in a case the district brought against federal regulation of water diversions from the Sacramento-San Joaquin Delta. The rules are meant to protect the Delta smelt, a threatened fish.

In an outburst from the bench in that case on Sept. 19, he accused two federal scientists of bias, calling one a "zealot" and suggesting the other distorted the truth. It was a rare emotional moment for Wanger, who for two decades has ruled for both water users and environmental groups in numerous complex water cases.

On retirement, Wanger became headline partner at a Fresno law firm that previously saw relatively little work in the water arena.

Wanger said he sees no conflict in taking the Westlands case.

"I would not undertake any representation where there is a conflict," he said. "Candidly, if the environmentalists had sought to hire me or the government had sought to hire me and I had no conflicts, I would have been happy to consider representing them."

Wanger is also representing Fresno County in its effort to prevent Occupy Fresno protesters from camping in Courthouse Park.

The new water case was filed in Fresno Superior Court in August by the North Coast Rivers Alliance, Friends of the River, Save the American River Association and the Winnemem Wintu Tribe. They allege that Westlands and the U.S. Bureau of Reclamation harm water quality and wildlife by irrigating Westlands land, which transports naturally occurring selenium from the soil into waterways.

Selenium can deform wildlife when it enters the food chain. It did so in spectacular fashion in 1983, when dozens of deformed birds were found at Kesterson Wildlife Refuge.

The plaintiffs are asking the court to require Westlands and the bureau to obtain a state waste-discharge permit.

"I guess I'm not surprised he's now basically retained by Westlands," said Steve Evans, program consultant at Friends of the River. "I'm sure Westlands is purchasing the best legal representation they can buy. But I trust the system to work, and I think we have a really good case."

Ethics rules forbid a former judge from serving as a lawyer for a party in a case over which he recently presided. That does not necessarily apply in a different case, even with similar issues. It may depend on details that can become a subject of legal dispute.

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