No one would mistake the Supreme Court’s liberal justices for adherents to the concept of “originalism,” or the belief that one should consider—first and foremost—the Founders’ intent when ruling on constitutional issues. And yet their opinions in the Maryland “Peace Cross” case suggests that they, at least implicitly, support the idea.

In American Legion v. American Humanists Association, the court upheld Maryland’s Bladensburg Cross against the claim that its presence on public property violates the establishment clause of the First Amendment. Writing in dissent, no less a figure than Justice Ruth Bader Ginsburg—the Notorious RBG and hero of the American Left—turned to the thought of the Founders in order to find the meaning of the establishment clause.

The original meaning that conscientious judges should seek is the meaning as it was understood by the public at large when the Constitution was ratified, and not the personal political views of selected Founders who, we should be reminded, were not sovereigns. Nevertheless, it is worth noting that no less a liberal giant than Ginsburg is willing to use at least some form of originalism in an effort to find the meaning of the Constitution.

Nor is this an isolated case. In the previous decade, when the court grappled with the meaning of the Second Amendment in District of Columbia v. Heller (2008), both the conservative and liberal justices turned to the Founding generation to understand the meaning of the “right to keep and bear arms.” Justice Antonin Scalia and the conservative majority found that the weight of the historical evidence supported an individual right to keep and bear arms, while the liberal dissenters disputed this conclusion.

Notably, however, the “living Constitution”—which some liberal commentators treat as the common sense alternative to the much-derided originalist line of inquiry—made no appearance in Heller. Justice John Paul Stevens and the liberal dissenters never suggested the meaning of the Second Amendment should be interpreted in light of today’s values. They mounted no attack on originalism itself as a mode of interpretation. Instead they countered with their own originalist investigation, looking at the same evidence and holding that it supported the view that the Second Amendment aimed merely to protect the state militia.

As well they should. Constitutional originalism provides a nonpolitical standard for judges, one that permits them to think beyond their own policy preferences. Its liberal detractors may claim that it is just a clever disguise for their own political judging (“Originalism is a scam,” according to one recent ThinkProgress headline), but their argument is a weak one.

Anyone who studies the early history of the American Republic can see that originalism is not some novel invention of modern conservatives but a long-established and venerable approach to constitutional interpretation. In his celebrated opinions for the Supreme Court, John Marshall—the “Great Chief Justice”—sought the original meaning of the constitutional provisions on which he was called to rule. Certainly Marshall never suggested—unlike the modern purveyors of the “living Constitution”—that the meaning of constitutional provisions could change over time or might be imbued with new meaning by the jurists of the present generation.

James Madison—the “father of the Constitution”—expressly endorsed originalism as a method of constitutional interpretation. In an 1824 letter to Henry Lee, Madison held that in seeking a “just construction” of the Constitution we must turn to “the sense in which the Constitution was accepted and ratified by the nation.”

“In that sense alone,” Madison added, “it is the legitimate Constitution. And if that be not the guide in expounding it, there can be no security for a consistent and stable, more than for a faithful exercise of its powers.”

Small wonder, then, that even liberal justices sometimes draw on originalist traditions. In light of that fact, liberal pundits ought to be candid enough to admit that originalism is not some cynical conservative expedient but a legitimate method of constitutional interpretation.

Perhaps they can go a step further and ponder the following question: If originalism is good enough for some areas of constitutional inquiry, why isn’t it good enough for all of them?

According to Ginsburg, the establishment clause intends to create a “wall of separation between Church and State.” Like generations of liberal judges before her, Ginsburg here relies on Thomas Jefferson’s understanding of the purpose of the establishment clause, expressed in his famous letter to the Danbury Baptists. Ginsburg and her predecessors additionally lean on James Madison’s arguments in the Memorial and Remonstrance, written against a proposed system of state support for religion in Virginia.

As it happens, this is a kind of originalism. It’s just that it’s a sloppy and tendentious form of originalism.