What is a man? For El’Jai Devoureau, this is not a rhetorical question.

Mr. Devoureau, who was born physically female, is a man at the Motor Vehicle Commission, at the Social Security office, at home, at job interviews. But what about at the urinal?

In a case with a truly unusual set of factors, Mr. Devoureau filed a discrimination lawsuit on Friday that could break new ground in New Jersey and across the country, turning on the question of who is or is not a man. An employer fired Mr. Devoureau because it said only a man was allowed to do his job: watching men urinate into plastic cups at a drug treatment center.

Mr. Devoureau, 39, says he has identified himself as a man all his life. In 2006, after he began taking male hormones and had sex-change surgery, he adopted the name El’Jai (pronounced like L. J.). A new birth certificate issued by the State of Georgia identifies him as male, as does his New Jersey driver’s license, and the Social Security Administration made the change in its records.

“As long as I’ve been a person, I’ve lived as a man,” he said in an interview. “At age 5, I did everything a boy did: I climbed trees, I played football, I played with trucks. Most of the people in my life, all they know is I’m male.”