“Originalism has been the reigning constitutional theory of legal conservatives since the election of Ronald Reagan,” a contributor to the National Review wrote recently, with glowing approval. The theory, which views jurisprudence as frozen in time, flatly rejects the idea of the Constitution as a a living and evolving document and instead demands that we interpret its provisions exactly as the framers intended.

This week, what was once a fringe intellectual concept, confined to conservative legal circles, achieved its ultimate ascendance. In a decision that purports to rely on deep historic knowledge of the founding generation’s views on gun control, the conservative majority on the Supreme Court knocked down a New York State law limiting the concealed carry of firearms. Drafted by Justice Clarence Thomas, the decision applies a strict originalist frame to conclude that “[o]nly if a firearm regulation is consistent with this Nation’s historical tradition may a court conclude that the individual’s conduct falls outside the Second Amendment’s unqualified command.’”

Thomas’ decision, endorsed by his five Republican-appointed colleagues, builds on the court’s earlier, originalist decision in District of Columbia v. Heller, which located in the Second Amendment an individual constitutional right to own firearms.

There’s just one problem. Both decisions get the history wrong.

There is ample reason to disagree with originalism as a legal philosophy. Should a 21st century society really interpret its Constitution by the standards of 1787 — an era before the introduction of semi-automatic weaponry, steam power, penicillin, automobiles, trains, electric lights and indoor plumbing? In some ways, though, that’s a pointless debate at the moment. With originalists holding six of the Supreme Court’s nine seats, we’re all living in an originalist world.

The functional problem with originalism is that it requires a very, very firm grasp of history — a grasp that none of the nine justices, and certainly few of their 20-something law clerks, freshly minted from J.D. programs, possess.

It’s difficult to become an expert in American political, legal or social history. It’s quite easy, though, to cherry-pick historical examples that prop up an end in search of a rationale — which is precisely what the Supreme Court majority did this week, twice.

In its recent gun control decision, just like in its recent abortion decision, the Supreme Court’s majority showed just how intellectually fragile the originalist project really is.