Imagine a world where employers can legally require women to “walk, talk, and dress more femininely” if they want a promotion. Or where managers can freely fire a woman because her face “looks too aggressive” or because they suspect her responsibilities at home mean she won’t be dedicated to her work.

Fortunately, US discrimination laws forbid this kind of behavior. But on Tuesday, the US supreme court hears arguments in a trio of cases that may call into question these basic protections. In one, a transgender woman was dismissed from her job as a funeral home director and in the others, gay men lost their jobs as a skydiving instructor and a child welfare services coordinator. The common thread? These individuals were fired because their employers did not want women or men “like that” in their workplaces.

Although these cases may seem to be only about LGBT rights, the reality is that everyone stands to lose basic workplace protections against discrimination if the court rejects these workers’ claims.

In 1989, the US supreme court ruled that “sex discrimination” includes situations where employers make demands of women that they would not make of men, like requiring women to match their view of how women should be in the workplace. Ann Hopkins was the plaintiff in that case against the accounting firm Price Waterhouse. She had been denied partnership as a management consultant – not because of her skills or work ethic – but because some in leadership thought she was “macho and pushy”, with one male partner advising her to take “a course at charm school”.

The court’s ruling 30 years ago – that employers may not rely on sex stereotypes to limit women’s opportunities at work – meant that women could push back against the glass ceiling, which a federal commission once defined as “the unseen, yet unbreachable barrier” that impedes the success of women and minorities at work.

And many did push back. Numerous lower court cases have granted claims by women who lost work or promotions because their “looks” did not meet their employers’ image of femininity or because they were seen as too aggressive. Men have also won cases where they were bullied on the job for not being masculine enough. Transgender employees have likewise won claims after their employers – including the Library of Congress, a fire department, and an auto repair shop, among others – fired or refused to hire them because they did not fit with the employer’s views about how men or women should look and act.

But the federal government, through the Department of Justice, makes arguments that would cut holes in these protections. It asserts that a transgender woman can be lawfully fired if an employer says she is not a “real” woman, and that a gay man can lose a job for not conforming to an employer’s view about “real” men. These kinds of stereotypes about women and men, the government says, remain fair game.

In short, three decades after the supreme court recognized that workplace decisions based on stereotyped views about men and women run contrary to our sex-discrimination law we may be on the cusp of taking a giant step backwards. To think that we are now questioning whether employers should have a “free pass” to rely on sex stereotypes is mind-boggling, even more so at a time of growing awareness about the pervasiveness of sex discrimination at work.

We cannot ignore what these three cases, and the social and legal questions they present, are really about: the rights of everyone to work free from the limitations of sex stereotypes. Against that backdrop, employers that fire or deny promotions because a transgender woman does not look like what the employer wants a woman to look like, or a gay man does not have a home life that his manager thinks a man should have, are little different from a boss who tells a female employee she’s fired or not being promoted because she’s not wearing enough makeup and acting ladylike. This is why 30 women who are CEOs and c-suite executives at companies across the country, including Shonda Rhimes and Sheryl Sandberg, filed a brief with the supreme court in these cases.

This is not ancient history, as we know from the many court cases filed by women and men who have lost opportunities at work, and from data showing that the number of women in leadership positions still lags behind men and that men continue to outearn women throughout the US. The proposed “free pass” for sex stereotypes puts at risk our nation’s sex discrimination law and the tens of millions who depend on it every day at work.