A recent editorial in the Tallahassee Democrat reported on, and praised, the students at Leon High School, who elected two women to serve as prom king and queen. The two women had dated for three years and were viewed by their peers perhaps as the most popular couple. The surprising part of this story was that after the story reached over 200,000 people on Facebook, many of the comments were supportive and celebratory, or expressed the simple idea that this was no big deal.

But this story is the exception, as we see uproars across the country to people, rules, and events that challenge conventional gender norms. When students at a California high school tried to elect a lesbian couple as prom king and queen, school officials issued a royal edict that for all-important prom purposes, qualification for “king” or “queen” is defined by sex at birth. Meanwhile, across the country in Harrisburg, Pennsylvania, a girl who showed up in a tuxedo was turned away at the prom door for violating the established dress code that says “girls must wear formal dresses.” And in nearby East Haddam, Connecticut, boys and girls walk in different lines at commencement, with boys dressed in blue, and girls in virginal white carrying flowers (discussed in detail here).

And if all this seems trivial—rules that affect people on only one night in high school—recall the sweeping (and unconstitutional) law passed by North Carolina recently, requiring that transgender individuals only use public bathrooms that align with their birth sex and wiping out the state’s protections against employment discrimination simply to ensure that no LBGT person ever benefited from them (discussed here). Or remember that the state refused to comply with a federal order stating that the bathroom portion of the bill violates Title IX and must be repealed. Or take notice of the efforts of Oklahoma legislators—at the same time they were passing an unconstitutional bill to ban all abortions (vetoed by their governor)—to pass a law that would grant students a right to avoid sharing a bathroom with a transgender student in the name of religious freedom.

Why all the hubbub? People simply cannot care this much about what people wear to a high school dance, whether the prom king is a boy (particularly when the students themselves don’t care), or whether girls are both differentiated and robed in pristine white at a high school graduation.

Now people might care about sharing bathrooms with transgender people, but only because they are misinformed, acting out of a misplaced fear of predation, or bigoted. The transgender bathroom problem has been framed in some circles as one as one of safety—protecting girls and women from bathroom predators. But there is no empirical support for this fear. The number of transgender people is very low—the best estimate, by the Williams Institute, is that a mere .3 percent of the population is transgender. But, more importantly, as Mark Joseph Stern recently pointed out on Slate, there is “overwhelming evidence and professional consensus” that this fear is entirely baseless. (Not to mention that, with or without laws protecting transgender access to bathrooms, predatory men could dress up as women and enter women’s rooms. Or, of course, they could just prey on little boys like Jerry Sandusky and Dennis Hastert, both of whom used all-male locker-rooms as their hunting grounds. But nobody is banning men from using communal restrooms).

There must, then, be some reason underlying all these scandals and stories. The real reason, we suggest, is that transgender people present a direct challenge to the existence of a simple division between the sexes. People who were born with one set of sexual organs but identify and present as members of the opposite sex blur the lines between sexes, and make clear there that the relationship between sex and gender is complicated. It’s hard to maintain sexual inequality when you can’t tell, exactly, what makes someone a boy or a girl, a man or a woman.

And when people are not transgender, but simply refuse to be segregated by sex or to conform to conventional sex norms, society has the same reaction: “make sure we can tell the difference between girls and boys.” When the girls in East Haddam wrote an opinion piece in the local paper, it met with scores of angry comments (now deleted) about how their efforts to change the school’s discrimination graduation robe policy were frivolous or stupid. But that argument cuts both ways. If it doesn’t mean anything, then why don’t the boys and girls wear the same graduation robes? Why wouldn’t the default be that everyone earning the same degree wears the same genderless attire in the ceremony to honor their achievements?

The absurdity of this argument was on full display in the early fight for marriage equality. After the Massachusetts Supreme Judicial Court ruled in Goodridge v. Department of Public Health (2003), that it was a violation of the state constitution for the state to deny marriage licenses to same-sex couples, the state senate passed a civil union bill—a marriage-equivalent status with a different name—and asked the court for an advisory opinion as to whether its actions had satisfied the judicial mandate. After all, the senate argued, it’s the benefits of the status that matter, not the name. But, in its response, in which it roundly rejected the legislative effort to avoid compliance with the original ruling, the state’s highest court dismissed the argument that this was merely a “squabble over the name to be used.” If the name didn’t matter, the court pointed out, then the senate would never have made such purposeful efforts to circumvent the court’s mandate. It was exactly the name that mattered because marriage of two women or two men would not allow for perpetuation of conventional gender roles.

But while the Massachusetts court was able to see the absurdity of the senate’s argument—and to insist on the full recognition of the substantive right it had declared—we collectively seem unable to do the same.

The law of dress codes under Title VII is perhaps the best example of our collective unwillingness to blur gender lines. Sex-specific dress and grooming codes have been challenged under Title VII, which bans all forms of sex discrimination by employers, since the mid-1970s. Title VII prohibits employment actions “based on sex,” making no exception for specific types of discrimination or “de minimis” inequalities. Yet, there has been a longstanding anomaly in Title VII case law that permits employers to maintain sex-specific dress and grooming codes. In an early case, Willingham v. Macon Telegraph Publishing Company (1975), a federal appellate court upheld a rule requiring men (and only men) to have short hair, while women were permitted to wear theirs long. The court refused to acknowledge the stereotypes reflected in the rule, observing simply that hair length was not immutable, and men could comply with the rule simply enough by just getting a haircut. Other courts have upheld policies requiring men to wear business suits and ties, while requiring women to wear dresses. They have also allowed employers to impose requirements that women wear makeup, while prohibiting men from doing the same thing.

These decisions are fairly described as anomalous because they seem to permit precisely what Title VII forbids: treating employees differently on the basis of sex. (Color-coded graduation robes present the same problem under Title IX, which forbids sex discrimination in education.) And the reasoning courts offer is generally unconvincing, circular, and employs the very same stereotyping that led the employers to adopt the rule in the first place. In Willingham, for example, a case that could easily win a worst-reasoned-opinion contest, the court stated that discrimination laws generally protect people based on immutable characteristics—on the theory that people should not be arbitrarily disadvantaged because of something they can’t change. And hair length, the court noted, is mutable, not immutable. But of course hair is not the alleged basis for discrimination, sex is. And sex cannot easily be changed. Courts in dress code cases resort to platitudes about “good business” and employer latitude to run a business the way it sees fit—the same way high schools cite “tradition” in support of gendered graduation requirements with no pedagogical justification.

But the thrust of anti-discrimination law is to override the decisions of employers that unfairly disadvantage certain groups of workers, regardless in most cases of the impact on business. And to overhaul those educational traditions that operated to the systematic disadvantage of women and girls. We do not, for example, allow employers to hire only white workers even if customers prefer them; nor do we allow employers to fire older workers and replace them with younger ones based on the stereotype that they will be more energetic and efficient. (And we would not allow a high school to line up black students on one side of the arena and white students on the other—or permit them to assign different color gowns by racial group.) But courts actually convince themselves that sex-specific dress and grooming codes are gender neutral as long as they adhere to generally accepted community standards, even if those standards are themselves the product of sex stereotypes.

The dress code law should have changed after the Supreme Court’s 1989 decision in Price Waterhouse v. Hopkins, in which it held that sex stereotyping is a form of illegal sex discrimination. A logical extension of that ruling might be that sex-specific codes are invalid if they reflect, reinforce, or perpetuate gender stereotypes. But courts continue to cite Willingham and similar cases for the proposition that dress codes are more or less off limits unless they impose an undue burden on one sex.

A less obvious, but still relevant, example of our collective urge to keep gender lines intact is in the battle over marriages by same-sex couples. Although the initial arguments against same-sex marriage had the appearance of real arguments—worry about the impact on children, for example—as opponents began losing the war, the arguments became more desperate and more ridiculous. Near the end, the opponents were making the “accidental procreation” argument—that heterosexual men need marriage in order to tame their wild sexual proclivities and to tie them to the women they impregnate, while gay men and lesbians more naturally find themselves in committed, purposeful relationships and thus do not need marriage. Yes, the argument was as ridiculous as it sounds. But, more importantly, it signaled the desperation opponents felt to maintain the tradition that men marry women, and women marry men.

What all these things have in common is that they are attempts to police the gender line. Maintaining the distinction between men and women wouldn’t be important if, for most everything, they weren’t treated differently. That is, when equality is the rule, then drawing a distinction really doesn’t matter—whether you’re on one side of the gender line or the other (or somewhere in between), you’re treated the same. At home. At school. At work. At church. At the country club. The distinction matters precisely because equality isn’t the rule in many of those places—the gender division reflects a longstanding hierarchy, with men on top. And if we can’t tell who’s who because people challenge gender conventions—by wearing the wrong color, or marrying someone of the wrong gender, or, even worse, trying to become someone of the other gender, chaos ensues.

This kind of behavior is not unique to sex discrimination. Systemic racial oppression depends, too, on a policing of boundaries. The “one drop” rule is the most notorious example. But a key facet of any system of oppression is the ability to clearly distinguish between classes of people. Any impediments to those distinctions, or suggestions that, even if they do exist, they don’t really support the kind of radical distinctions that get drawn in the law or, more generally, society, are dismissed.

This isn’t to say that people who are gay, transgender, or graduating from high school aren’t being independently targeted for discrimination. They are, and their suffering is real. But they are also pawns in a larger game of gender oppression, one that depends on having clearly drawn battle lines.