In 1992, for example, the E.U. proposed a package of protections for pregnant mothers in the workplace and set a minimum for maternity leave known as the Pregnant Workers Directive, forcing Britain to crystallize them in its domestic laws. In 1998, under former Prime Minister Tony Blair, Britain adopted the E.U.’s Working Time Directive, which guaranteed workers at least 20 days of paid vacation.

“The E.U. has been a very positive actor in the development of gender equality policies in the U.K.,” Guerrina said.

The question now is: What happens to this patchwork of laws once Britain leaves the E.U. and is left to its own devices?

Former Prime Minister Theresa May had included a commitment in her withdrawal agreement(s) to maintain those protections after Brexit, Stephenson said.

But when Boris Johnson replaced May as prime minister in June, he moved that language over to the so-called “Political Declaration” — a non-legally binding document that is widely seen as an “aspirational piece of paper that explains where the government would like to be with the European Union,” said Mujtaba Rahman, a former European Commission official who works for the consultancy Eurasia Group.

In other words, many of Britain’s standards and protections for women that were once guaranteed by the E.U. can theoretically be repealed, leaving them vulnerable to the whims of not just this government, which has repeatedly promised to deregulate industries and cut back on red tape for businesses, but future governments, too, with no higher-level checks and balances.

Johnson’s government has signaled it will remain aligned with the E.U. on this front and maintain many of those rules, Rahman said, but “there’s a lack of trust.”