The Biden administration had argued, in the course of its participation in a lawsuit against Tennessee’s law barring transgender-based treatments for children, that

A teenager whose sex assigned at birth is male can be prescribed testosterone to conform to a male gender identity, but a teenager assigned female at birth cannot.

The Supreme Court last week issued its ruling that the Tennessee law was, in fact, perfectly fine; the ruling was 6-3, with the three activist Justices voting in dissent. Chief Justice John Roberts wrote the Court’s opinion, and Justice Amy Coney Barrett wrote a concurrence centered on answering one of the objections in the dissent. Justice Clarence Thomas wrote a separate concurrence in which he took to task all the plaintiffs’ demand that the Court knee-jerk accede to so-called experts in the Executive Branch regarding transgenderism.

However, it would have been good if the Court had addressed one more item—the Biden administration’s false premise underlying its argument.

That erroneous premise is this: that sex is assigned at birth. This is blatantly false. Sex is assigned at the moment of conception, when the male sperm, carrying either an X chromosome or a Y, joins with the egg and its X chromosome. The subsequent union, the zygote, is then deterministically a male with an XY combination or a female with an XX combination. That male or female—boy or girl—result is carried on through subsequent development all the way through fetus development and birth. The sex determination is immutably fixed at that first moment of union; it is not “assigned” later.

Had the Court put that underlying false premise to bed, also, would have obviated a myriad arguments (legal, anyway) about the origins of an individual’s transgender situation.