With North Carolina’s move to ban transgender people from certain public restrooms, public bathrooms have once again become a civil-rights flashpoint. Photograph by MANDEL NGAN / AFP / Getty

On Monday, Loretta Lynch, the U.S. Attorney General, and Pat McCrory, the governor of North Carolina, announced that they would be suing each another over the Public Facilities Privacy & Security Act, a new law requiring that North Carolinians use only the public bathrooms that correspond to the “biological sex” listed on their birth certificates. In Texas, a parallel conflict began brewing between the retailer Target, which has announced an open-bathroom policy for transgender employees, and the state’s attorney general, Ken Paxton. (Paxton has demanded, in a letter to Target’s C.E.O., that the company provide the full text of its “safety policies regarding the protection of women and children from those who would use the cover of Target's restroom policy for nefarious purposes.”) And in Chicago, a legal battle is being waged over which high-school locker room a transgender student ought to use. Yesterday, the Obama Administration issued a directive telling all public schools to allow students to use bathrooms or locker rooms matching their gender identities. Across the country, in other words, controversy is following transgender people who step into sex-segregated spaces.

This is familiar territory for Sheila Cavanagh, a professor of gender-and-sexuality studies at York University, in Toronto. Almost ten years ago, Cavanagh was teaching a graduate seminar on gender and sexuality. She’d assigned Freud’s “Three Essays on the Theory of Sexuality,” but her students kept talking about bathrooms. “I thought they were so off-topic,” Cavanagh recalls. “Then I thought, Maybe I’m the one who’s off-topic.” Cavanagh began to think about the many stories she’d heard from queer and transgender friends about being harassed for going to the “wrong” bathroom; in 2010, she published a book based on interviews with one hundred L.B.T.Q.I. bathroom-goers, called “Queering Bathrooms: Gender, Sexuality, and the Hygienic Imagination.” I spoke to Cavanagh by phone earlier this week, hoping that she could explain why and how bathrooms have become a civil-rights flash point.

All of a sudden, non-trans people are talking about transgender people using gendered bathrooms. But I assume that transgender people have been talking about this for a long time.

Right—it’s an old issue. People who are transgender or gender-variant, or who are perceived to be gender non-conforming, have always had difficulties in gendered bathrooms. And, if you think historically, you realize that we’ve always used bathrooms to segregate people. Up until the sixties, you had racially segregated bathrooms in the United States. We’ve only recently begun to build accessible bathrooms designed for people with mobility issues. So we’ve always used bathrooms to enforce social boundaries.

How does not having access to a bathroom—or not feeling welcome in the bathroom you want to use—affect a person's life?

If you can’t use the bathroom, it’s harder to go to school, to go to work, to buy groceries, to do things that many of us who are cisgender take for granted. It’s a real issue. I have discovered that a lot of people who are transgender don’t drink enough water over the course of the day. Because of the obstacles they face, they’ll go to great lengths to avoid using public bathrooms.

Many of those who want to regulate bathroom access for transgender people cite safety concerns. They say that bathrooms are places where people are vulnerable—especially children.

In my research, I haven’t uncovered a single example of a trans person physically or sexually assaulting or harassing anyone in a bathroom. I have, however, uncovered many examples of cisgender people, both male and female, harassing or assaulting those who are transgender. A lot of the trans people I interviewed told me that, when they used the women’s bathroom, it wouldn’t be uncommon for non-trans women to yell at them or hit them with their purses. What gets socially coded as fear is often just masked transphobia—people know that it’s less acceptable to be transphobic than it is to say, “I worry about the safety of my daughter.”

Opponents of transgender access often claim that they’re worried about people who_ _pretend to be transgender. For example, Ken Paxton, the Texas attorney general, has written about “those who would use the cover of Target's restroom policy for nefarious purposes.” They seem to be imagining a Peeping Tom scenario, in which the perpetrator is a cisgender man who, when confronted, claims to be transgender.

I think that’s a far-fetched fear not based on actual evidence. I haven’t encountered any examples in my research of a sexual predator dressing as a woman, or in feminine clothing, to prey upon a non-trans woman in a restroom or a gymnasium. Most feminist studies on violence against women have shown that the safest spaces are actually gender-inclusive spaces that are open-concept and well-lit, with more than one door so that people can enter and exit in at least two ways.

What is it about the bathroom? Why is it here—as opposed to, say, on a sports field—that controversy erupts?

Recently, I read a fascinating article by an American historian who did research on what happened in the early twentieth century when doctors discovered that there were high rates of gonorrhea among young girls. The obvious cause of gonorrhea was childhood sexual abuse and incest. But, for a long time, doctors were too afraid to accuse white, middle-class fathers of acting “inappropriately” toward their daughters. Instead, they said that many of these cases of gonorrhea must be the result of these girls using public toilets. So it often seems as though the bathroom holds our anxieties and contains the taboos we can’t acknowledge in other public spaces. Bathrooms are also one of the last officially gender-segregated spaces in Canada and the United States—and, because of that, they give those of us who are cisgender an opportunity to question and interrogate the gender identities of others in a way that’s more difficult to do in gender-inclusive spaces. In other words, the gender signs on the doors give people license to police the gender identities of others in ways that are overtly transphobic.

Many people who want to restrict bathroom access seem to feel that the very concept of gender is, in itself, under assault—that we are heading for a post-gender or genderless world.

Most people who are trans are not trying to undermine gender, or to do away with it. Transgender people do, however, challenge bi-gender culture, which assumes that there are only two ways of being gendered—you’re either masculine or feminine, and if you’re born female you’ll grow up to be feminine and vice versa.

Our bathroom regime is imperfect in many other ways: according to Harvey Molotch, a sociologist at N.Y.U. who’s written extensively about bathrooms, a truly equitable allocation of bathroom space would result in women’s bathrooms being two or perhaps even three times as big as men’s. So let’s imagine that we could start from scratch and create a bathroom utopia. What would it look like?

I suspect that bathrooms in the West will always be changing and adapting to our ideas about bodies. I don’t think we’ll ever settle on a “perfect” bathroom. Personally, though, I love bathrooms that play gently and creatively with gender in ways that prompt us to think outside narrow and prescriptive gender dichotomies. In Montreal, there’s a place called the Whisky Café which has, in the “women’s room,” a standing female urinal. On the wall beside the urinal there are instructions for use. The invitation to stand can be liberating.

This conversation has been edited for length and clarity.