The ruling by Britain’s top court that only those people born female can be considered women is a victory for reality — and the generation’s preeminent chronicler of witchcraft and wizardry, J.K. Rowling. At issue was the definition of “woman” in a 2010 law passed by Scotland’s Parliament mandating gender balance on public-sector boards. Scotland took the losing position that in this context transgender women ought to be considered females. 

The triumphant take belonged to Ms. Rowling, among others, who concurred with the court that the “ordinary meaning of those plain and unambiguous words” — woman and sex —  “corresponds with the biological characteristics that make an individual a man or a woman.” Put another way, the highest tribunal in the United Kingdom found unanimously that the terms “woman” and “sex” refer to “biological women and biological sex.”

Ms. Rowling was not a party to the case. It was won by a group called For Women Scotland. The creator of “Harry Potter,” though, has been among the stalwart supporters of the position on which the court landed. For that, she has received more vitriol than has been directed at He Who Must Not Be Named. She posted on X after the decision came down that it is owed to  “extraordinary, tenacious Scottish women with an army behind them.”

Is it a coincidence that Ms. Rowling referenced an army when the forces for good in her own seven-volume chronicle come to be known as “Dumbledore’s Army?” In any event Scotland took the opposing position, against her most famous — and richest — resident. Britain’s Labour party, though, hailed the ruling as delivering “clarity and competence” and the Tories marked it as a  “clear victory for common sense.” 

The high court’s deputy president, Lord Hodge, counseled “against reading this judgment as a triumph of one or more groups in our society at the expense of another, it is not.” He also insisted that it “does not cause disadvantage to trans people.” That distinction, and marks the line where fairness could tip over into bigotry. It also marks in sharp relief the contours of the kind of reasonable position that could be exported across the Atlantic.

The ruling from the UK high court comes as Attorney General Bondi announced a civil lawsuit against Maine for failing to comply with the administration’s mandate against transgender women competing in girls’ sports. Attorney General Bondi explained it like this, in prose that might not be Rowling-esque, but that works for us —  “Pretty simple: girls play in girls’ sports, boys play in boys’ sports. Men play in men’s sports, women play in women’s sports.”

Ms. Rowling helped fund the effort that triumphed at the court. The “Harry Potter” books have made her, by some measure, wealthier than King Charles. Somehow it doesn’t surprise that a woman who has spent her years bringing to life the world of mystery should have been ahead of the curve on this question. Dreaming of fictional worlds appears to have only strengthened Ms. Rowling’s ability to keep her focus straight in this one.