In the middle of taking the bar exam at the Jacob K. Javits Convention Center, in New York City, along with thousands of aspiring lawyers, I had to go to the bathroom. The enormous line for the women’s restroom looked like it would take at least a half hour. There was no line for the men’s restroom. I walked in, passed my male counterparts at a row of urinals, used one of several empty stalls, then returned to my desk. I felt that my decision to forgo the women’s bathroom made a difference to my passing the exam, and that the much longer wait for women than men during an all-important test for entry to the legal profession was obviously unfair.

There is now, however, an active debate around what bathrooms we should be able to use. A recently proposed Indiana law would make it a crime for a person to enter a single-sex public restroom that does not match the person’s “biological gender,” defined in terms of chromosomes and sex at birth. The punishment could be up to a year in jail and a five-thousand-dollar fine. Similar laws proposed in several other states have not passed. These proposals attempt to counter recent moves in many states to allow transgender people to access bathrooms that correspond to their gender identity. In the wake of the Supreme Court’s same-sex-marriage decision, last summer, these skirmishes may give the sense of moving the L.G.B.T.-equality debate from the sublime to the ridiculous. But the implications of the controversy go far beyond bathrooms.

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The connection of public bathrooms with condemned sexual behavior also relates to our recent history of criminalizing homosexuality. For most of the twentieth century, gay sex was criminal, and public disclosure of a man’s homosexuality spelled the death of his reputation and career. Public restrooms were sites of clandestine sex among men, and undercover police engaged in bathroom surveillance to catch men seeking sex in toilet stalls. David Sklansky, a law professor at Stanford, has argued that modern legal ideas of privacy were forged in the nineteen-sixties in part because of the Supreme Court’s distaste for this sordid police practice. According to his theory, bathroom sex is the “secret subtext” of Katz v. United States, which requires the police to have a warrant to eavesdrop electronically on a call made from a telephone booth, and is the source for the modern idea that the Constitution protects a reasonable expectation of privacy. Since Lawrence v. Texas, in 2003, it has been unconstitutional to criminalize gay sex taking place in private, but this protection does not apply to sex (gay or straight) in public spaces. As late as 2007, Senator Larry Craig was arrested in an airport-restroom sex sting for signalling interest in sex with a stranger in an adjacent stall, and convicted of disorderly conduct.