Cherie Blair, the outspoken wife of former prime minister Tony Blair, is campaigning to force the Garrick Club in London to admit women. The private club has been all-male since its founding in 1831. An internal vote of the membership in 2015 saw only 50.5 percent vote in favor of admitting women, short of the two-thirds needed to change the policy. Now female lingerie CEO Emily Bendell has launched a public petition and legal effort to obtain an injunction against the club under section 29 of the Equality Act of 2010 banning sex discrimination.

In announcing her public support for the petition, Cherie Blair called the no-women rule “outrageous.” She marveled that so little had changed since the first time she tried to enter the Garrick Club as a young trainee barrister in 1976, when she was turned away while her future husband was admitted.

We’ve learned a lot in the four decades since then. Among other things, we have learned that abolishing single-sex institutions has been far more costly to society than anyone in the 1970s predicted.

People underestimate just how much of American life used to be sex-segregated. The average suburban dad in the 1960s would have spent much of his free time in all-male organizations, from the Rotarians to his local golf or tennis club. Mom’s church committees were usually all-female in practice if not officially, as was the PTA.

That began to change in the 1970s and ’80s as feminists launched lawsuits to force institutions across America to go co-ed. The Rotary Club took its case all the way to the Supreme Court, where it lost in 1987. The Elks agreed to admit women in a settlement with the ACLU in 1995.

The rationale behind these lawsuits had to do with networking. It was all well and good for women to be hired by big corporations, feminists said, but they would be held back in their career advancement if they could not join in off-hours schmoozing.

The victims of discrimination second-wave feminists wanted the public to imagine were people like the female lawyer trying to make partner or the Yale professor handicapped in her quest for tenure by the no-women rule at Mory’s Temple Bar. But in fact these lawsuits frequently ended up targeting equally sympathetic defendants.

The California case Isbister v. Boys’ Club of Santa Cruz (1985) began when widow Ruth Mallery endowed a recreational club for boys in her neighborhood to commemorate her late husband’s lifelong interest in the problem of juvenile delinquency. An 8-year-old girl, Victoria Isbister, assisted by the local ACLU, sued the club. Not only did the California Supreme Court rule in Isbister’s favor, Chief Justice Rose Bird mocked Ruth Mallery as exemplifying “wealthy patrons who prefer to confer largess in a sexually discriminatory fashion” and “insulate a select few from the 20th century.”

Eventually organizations learned not to put up a fight. In 2019, the all-female coworking space the Wing chose to admit men rather than fight a sex-discrimination lawsuit brought by a 58-year-old man who had sought to join its Georgetown location in Washington, D.C.

Most anti-discrimination statutes permit exceptions in cases where it can be shown that excluding women is directly relevant to an organization’s purpose. However, these exceptions fail to recognize that single-sex spaces are a good in themselves.

In the Boys’ Club of Santa Cruz case, for example, the court ruled that keeping out girls had no relevance to the club’s purpose of providing recreation. But boys flourish in the company of other boys in ways that the presence of girls inhibits—this is perhaps especially true of the kind of boy otherwise at risk of becoming a juvenile delinquent. Men form deeper friendships in all-male groups, which may be why civil society organizations like the Rotarians that were legally compelled to go co-ed in the 1980s have gotten weaker ever since.

Feminists sneer that if there are jokes men were planning to tell at the club that they can’t say around their female colleagues, then maybe they shouldn’t be telling those jokes in the first place. This misses the point of single-sex spaces, which is not about off-color jokes but about basic principles of group dynamics.

It so happens that these differences have been studied extensively by (brave) psychologists and anthropologists, but we do not need experts to tell us what is obvious: Just as men are different from women, groups of men are different from groups of women. They operate by different rules and have different strengths and weaknesses. They vary in competitiveness, in whether decisionmaking is egalitarian and consensus-driven or hierarchical, in what kinds of conformity are enforced and how. It’s common sense. Unfortunately, common sense has been superseded by equal rights law—which, incidentally, is Cherie Blair’s world, as a lawyer specializing in human rights litigation.

Today the frontier of civil rights law is in forcing institutions to treat biological men as women if they identify as trans. It would be better if the momentum were in the other direction, not in forcing all-female spaces to admit biological men but in defending the right of single-sex institutions to exist at all. The relatively narrow range of spaces targeted by trans activists—bathrooms, saunas, prisons, sports teams—underscores just how few of these we have left.