The debate over transgender individuals and public facilities yields more heat than light. The Washington Post Outlook section thought it was providing perspective with a recent lighthearted spread on the long history of battles over public bathrooms. Not a word was said about the more problematic space: locker rooms.

Media discussions of the North Carolina law requiring use of accommodations consistent with the sex on one’s birth certificate rarely mention that in many states one can alter one's birth certificate after sex reassignment surgery. Of course, those who have undergone hormonal and surgical treatment to make their bodies more congruent with their gender identity cause less commotion in locker rooms appropriate to their identity. But many transgender people do not want to "transition" fully or at all. I sympathize with people who feel their biological sex is not who they are, but shouldn't we feel sympathy also for people traumatized by the sight of nude bodies that certainly appear to be in the wrong locker room? At one YMCA, a woman abused as a child told the Seattle Times that being seen in the shower by a transgender woman who hadn't surgically transitioned would reproduce the trauma she endured when her abuser enjoyed watching her in the shower.

In practice, laws intended to allow transgendered people to use the facilities of the gender they identify with will protect heterosexual men who simply like to expose themselves or look at nude girls and women. For a case that illustrates this danger, and the difficulties of formulating policy on transgender issues, consider what happened at a Seattle public swimming pool in February. A young adult male in men's clothes used the women's changing room before and after his swim, and he did not self-identify as female. Since girls' swim teams had practices on both ends of the man's swim, girls and women were undressing while he was in the changing room. Naturally, the girls and their parents became alarmed.

When staff asked the man to leave before he entered the pool, he replied, "the law has changed and I have a right to be here." After all, Washington state allows people who are biologically male to use women's facilities—if their gender identity is female. Staff again asked the man to leave when he was changing after his swim. He resisted at first, but eventually did so. But did those in charge of the pool have the legal right to challenge him?

Seattle Parks and Recreation communications manager David Takami thought his authorities dealt with the situation appropriately. Pool staff had not yet come up with a policy to protect everyone, and they did not have any guidelines in place for how people should demonstrate their gender before accessing a changing room. Instead, staff relied on people's physical appearance or verbal claims, and by neither standard did this man seem to be a transgender woman.

But surely proponents of transgender rights would object to any requirement that transgender persons report their gender identity to authorities before using their preferred facilities. Mandating that they verbally single themselves out in this way could cause embarrassment to many transgender people.

And we could hardly rely on individuals' physical appearance. As feminists and other progressives have been telling us for decades, women who resist pressure to dress and present themselves in a stereotypically feminine way are nonetheless women in every sense of the word. It can be impossible to guess the gender identity of someone who is biologically female but mannish in appearance.

Some may suggest protocols allowing only transgender people who have pursued hormone treatment and/or surgery to use the bathrooms and locker rooms of the gender they identify with. That wouldn't fly because so many transsexuals want to do neither.

The folks at the Seattle pool tried to take everyone's feelings into account. They offered the use of the family changing area to both the women who complained about the male in their locker room and the male himself. I would guess that, in the typical case, the family changing area would be too small to accommodate all the offended girls and women. But in any event, it was only the male who was pressured to leave the women's changing room. If he had been in fact a transgendered female, the authorities at the pool broke Washington's rules. State regulations forbid treating the feelings of transgender people and alarmed women equally: "If another person expresses concern or discomfort about a person who uses a facility that is consistent with the person's gender expression or gender identity, the person expressing discomfort should be directed to a separate or gender-neutral facility, if available."

In other words, if the man at the Seattle pool had been a self-declared transgendered female, the authorities should have followed the example of Washington's Evergreen State College. A few years back, parents of girls on a high school swimming team that practiced at the college pool complained about the presence of a transgender woman, Colleen Francis, in the women's locker room. Ms. Francis, who has male genitalia, was walking around the women's changing room when not lounging with legs asunder behind a glass door in the adjacent female sauna. She calls herself bisexual with a special attraction to women. The girls on the swim team were told that they could use a small changing area nearby while Ms. Francis used the larger women's room.

One writer on GenderTrender, a feminist site skeptical of the transgender movement, pointed out the Evergreen State situation was reminiscent of pre-Title IX America, when girls' sports teams frequently used facilities notably inferior to those available to male athletes: "The Washington state law is being used to attach a condition to Title IX equality for females, and that condition is that equal access to facilities for teenage girls is predicated upon their willingness to undress and shower in front of a self-described 'kinky,' 'horny' middle-aged heterosexual man who refers to himself as 'a teen girl.' "

In Washington state, the strong feelings of a number of girls and their parents count for nothing compared with the feelings of a single transgender woman with male genitalia.

Only about 0.03 percent of Americans are transgender. But in time, under the new regime, many males who are not transgender will be using women's rooms. That's because in the real world, many men—maybe most—like to look at naked women. Too many of these men get special pleasure from looking at undressed women who are unwilling to be, and frequently unaware of being, observed. Voyeurism, like exhibitionism, is an overwhelmingly male phenomenon.

Last year the Baltimore Sun noted a number of high-profile cases of video voyeurism. Featured was a rabbi who would routinely record women using a changing room at a Jewish ritual bath facility. One of his victims said she worried that the recordings could be posted online, and added that now whenever she uses a public restroom, she wonders whether she's being watched.

Dr. Sharon Moore, a psychiatrist specializing in trauma disorders, told the Sun that victims of voyeurism can suffer stress disorders or exhibit hypervigilant behavior as a result. And voyeurs are apt to be repeat offenders, she added. "It's something that makes people feel good, either from the power or the rush."

With the widespread availability of tiny, powerful cameras, it is easier than ever to get away with voyeurism and thus more tempting. Only a small percentage of voyeurs are caught. One voyeur in Florida said he observed more than 50 women trying on bathing suits in a department store over the course of six months before he was caught with a tiny camera at a peephole in an adjoining room. Imagine how much easier voyeurs will have it when they can put on a little lipstick, declare a female identity, and roam women's facilities all over the country.

Steven E. Rhoads is professor of politics emeritus at the University of Virginia and the author of Taking Sex Differences Seriously .