The American Civil Liberties Union has never been to all tastes, but it has always had the merit of astringent honesty. Free speech was the flagship cause, and it applied as much to Nazis as to anyone else. We can agree or disagree about the principle and its application but no one could doubt the historic sincerity of the ACLU in defending it. Now the ACLU freely says the following: “Men who get their periods are men. Men who get pregnant and give birth are men.”

Is this true? Of course not, but that’s not the point. What’s pressingly obvious is that to state this disagreement openly in Britain is to invite a police response, with, thus far, willing courts waiting behind them. How has this come to pass?

That a decade ago it was the opinion of no one that, upon mere act of will, men could be women and women could be men is demonstrated by it not even being a Liberal Democrat manifesto promise. Across the English-speaking world, progressive politicians from the Clintons to Obama rebuffed the case that transgenderism accepts as fact today, and policemen investigate if contradicted.

The excellent “Fair Cop” initiative is currently fighting this. Their cases are exemplary. Take former police officer Harry Miller, whose tweeted doggerel drew the attention of serving officers. “Were any of the tweets criminal?” Mr Miller had the presence of mind to ask the constable who telephoned him. “No,” replied PC Gul. “Then why are you ringing me?” asked Mr Miller. “I need to check your thinking,” said PC Gul.

Even success at the high court for Fair Cop will not prevent banal statements of biological facts from being potentially criminal acts. At the Lib Dem Equality and Human Rights election launch event our political editor asked Luciana Berger and Chuka Umunna whether there would be any medical tests for a change of sex under their plans.

Neither answered this point of detail — theories, not facts, are the strong point of this mania — but Lib Dem president Sal Brinton instead regretted the failure of the current Conservative government to implement its plans: “We are very clear that earlier this year when the government put out a consultation on the Gender Recognition Act that we wanted to see that everything that was in that consultation was in place.”

There is, on this issue, not much in the way of choice between the parties standing for election. The 2004 Gender Recognition Act requires that for a change of sex to be legally recognised, the applicant must undergo a (nonphysical) medical diagnosis for gender dysphoria and to have spent two years living in their preferred gender.

Detail is of the essence. The proposition is that men can become women and women can become men. How and when are pertinent words

To put it mildly, these are neither stern nor precise tests, are less so every passing day, and require ever more courage from would-be dissenting doctors. The Lib Dems plan to scrap even the pro forma medical diagnosis. They make no mention of the two-year requirement, and, as we have seen, decline to offer detail on how the magical thinking would work and regret that the Tory government’s highly agreeable, to them, plans were forestalled by the election.

It is necessary not to be squeamish on this subject. Former Labour politicians now in the Lib Dems might retain the innate big party prudence to say nothing when tasked with difficult, detailed questions on this subject, but detail is of the essence. The proposition is that men can become women and women can become men. How and when are pertinent words.

Much like a fairytale stork delivering a new-born infant, we are not to know precisely how the wonderful event happened. It just did, though once it has, it must be implacably defended in law. It moves from discretionary fancy to hard, yet hazy, fact. Which brings us to when: when do people transition? For if transgenders are to be afforded the protection of the state for having transitioned, however that’s accomplished, necessarily a start date is required. You can’t get the goodies until we know what you are.

Women, foolishly lacking such “protected characteristics”, will not get these boons, but transgenders will. So when? When they say so seems to be the current correct thinking. And just saying so is what this turns on. It shows how the practices of the state outrun the law, and it explains why policemen police opinions in modern Britain, with every expectation that judges will back their excesses.

A ragbag of curiously drafted piecemeal legislation, advocated and advanced without any sustained scrutiny, has given bureaucracy, police and courts a chance to do right, as they see it. The very imprecision of their cause is what affords them this opportunity: clarity as to its supposed central act — transition — would end it in an instant. Common sense says that if a thing can’t say when and how it happens, it hasn’t happened. It’s time politicians let this be said by everyone.