Brian Prowel is effeminate. He crosses his legs and swings his foot. He files his nails if one has a snag. He has a high-pitched voice.

He is also gay. He has a rainbow decal on his car and he talked about the men he was dating at work.

On Feb. 23, 2006, Mr. Prowel filed a federal lawsuit against his former employer, Wise Business Forms Inc. in Butler County, alleging sex discrimination.

He argued that he was discriminated against because he did not live up to his co-workers' stereotypes of how a man should look and act.

U.S. District Judge Terrence F. McVerry dismissed Mr. Prowel's claims, saying that he was discriminated against not because of his sex but because of his sexual preference -- something that is not covered by federal law.

The case will be argued before the 3rd U.S. Circuit Court of Appeals Wednesday.

If the opinion stands, according to women's advocacy groups, it could have detrimental effects on gender equality in the workplace -- specifically for women like construction workers or firefighters who work in non-traditional occupations.

"We're very worried there's going to be a big hole blown into the side of the protections these women typically get," said Susan Frietsche, senior staff attorney with the Women's Law Project in Pittsburgh.

Title VII is the federal law that prohibits discrimination based on sex, religion, race and national origin.

Included in the subsets of sex discrimination is gender stereotyping.

Not included, however, is harassment based on sexual orientation. Though Congress has tried to pass such a bill several times, none has ever made it through both houses. As a result, discrimination based on sexual preference is handled piecemeal.

For example, discrimination based on sexual orientation is prohibited in the city of Pittsburgh, but not in Allegheny County. It is prohibited in New Jersey, but not in Pennsylvania.

In his 15-page opinion, Judge McVerry called the behavior Mr. Prowel was subjected to "reprehensible."

But, he continued, it was not sex discrimination.

Mr. Prowel worked for Wise from 1991 through 2004 on a machine that numbered and stacked forms, mostly for bank transactions.

Co-workers called Mr. Prowel "Rosebud," and "Princess." Someone left a feathered tiara on his workstation along with a packet of personal lubricant. Graffiti was written about him on the bathroom walls.

Judge McVerry found that those were all examples of discrimination because of Mr. Prowel's sexual orientation.

But his attorney, Timothy P. O'Brien disagrees.

Making fun of Mr. Prowel for being effeminate, calling him "Princess," and giving him a tiara all "smack" of gender stereotyping, Mr. O'Brien said.

More than that, he believes that whether the harassment was based on gender stereotyping or sexual preference, it is still a decision to be made by the jury and not a judge.

Joanna Grossman, a visiting law professor at Vanderbilt University and an expert in sex discrimination, said that judges often get bogged down by trying to make a specific set of facts fit into a unique category.

"Most people who are discriminated against or harassed at work -- it's not really just for one thing," Ms. Grossman said. "The fact is, it's probably both -- sex discrimination and sexual orientation.

"That's probably where a jury would do a better job. They would recognize the complexity."

It was a 1989 U.S. Supreme Court decision that first made clear that gender stereotyping is prohibited by Title VII.

"They can't make women act feminine, and they can't make men act masculine," Ms. Grossman said.

The Prowel case is a prime example of that, she said.

"This is exactly the same as a woman in a non-traditional job being pushed out because she acts too much like a man," Ms. Grossman said.

Ms. Frietsche, who wrote a lengthy friend-of-the-court brief on Mr. Prowel's behalf, said that women continue to be subjected to horrific harassment when they work in positions that don't conform to gender stereotypes.

"If the reasoning of the district court in this case is upheld, however, employers who seek to lock women out of these well-paying fields could evade Title VII liability through the simple expedient of lacing their gender discrimination with enough anti-lesbian slurs," Ms. Frietsche wrote.

In her brief, she said that Judge McVerry's opinion was wrong and would have a negative impact on women's struggle for equality in the workplace.

"With minimal analysis, the district court disregarded this evidence of classic gender stereotyping, conflating it with evidence of anti-gay prejudice and misconstruing Mr. Prowel's complaint as nothing but an artfully pled claim of sexual orientation discrimination."

She also cited another Third Circuit case from 2001, in which the court found that gender stereotyping can stand as a claim, even where there is evidence of sexual orientation discrimination.

"Simply stated, employers cannot immunize themselves against sex discrimination claims by hiding behind their anti-gay or anti-lesbian prejudice," Ms. Frietsche wrote.

Mr. O'Brien believes that his client's case could have huge consequences on employment discrimination law.

"It has ramifications considerably beyond what happened to Mr. Prowel," he said.