The idea that the meaning of a constitutional provision is frozen at the moment of its ratification—and that its meaning can be discerned and applied to contemporary controversies in an incontestable manner—lies at the heart of arguments for originalism, an interpretive method Supreme Court Justice Antonin Scalia has spent his career championing.

But both judicial and popular conceptions of constitutional meaning undeniably change over time, and there is often disagreement over how to understand the historical evidence. Ironically, nothing illustrates this more powerfully than the recent history of the Second Amendment—the subject of Justice Scalia’s most avowedly originalist opinion for the Court and an issue very much on the minds of both Congress and the people in the wake of tragic shootings from Connecticut to Arizona and in between. Recent gun control proposals in the Senate foundered in part over concerns that expanded background checks would breach protections supposedly enshrined in the Constitution.

Yet in 1991 former Chief Justice Warren Burger called the claim that the Constitution protects an individual’s right to possess a handgun “one of the greatest pieces of fraud—I repeat the word ‘fraud’—on the American public by special interest groups that I have ever seen in my lifetime.” Chief Justice Burger embraced what had been the consensus view among federal courts throughout the 20th century: when the framers wrote, “A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed,” they were protecting the ability of individuals to participate in organized state militias. Thus, for example, in United States v. Miller (1939), the Supreme Court rejected two defendants’ claims that the Amendment protected their right to possess a sawed-off shotgun. The Court found no evidence that owning such a gun “has some reasonable relationship to the preservation or efficiency of a well regulated militia.”

But Justice Scalia’s opinion for the Court in District of Columbia v. Heller (2008) adopted a very different view of the Second Amendment, holding that it “protects an individual right to possess a firearm unconnected with service in a militia.” The decision reflected a dramatic shift in constitutional understanding.

So what changed between 1991 and 2008? Clearly, not the words of the Second Amendment. Nor did historians discover some previously unknown eighteenth-century documentation of the amendment’s meaning. To be sure, during the intervening years some legal and historical scholarship advanced arguments for an individual-rights, rather than a collective-rights, approach. But many leading historians of the period continue to adhere to a collective-rights interpretation. And as legal scholars such as Adam Winkler (in his magisterial 2011 book Gunfight) and Reva Siegel have shown, the triumph of the individual-rights approach in Heller is part of a larger story of cultural change and political struggle that simultaneously transformed popular understandings, scholarship, and the membership of the Court.

That being said, what divided the Court in Heller was not primarily interpretive method. Both Justice Scalia and the dissenters in the 5-4 decision devoted a great deal of attention to textual exegesis and historical inquiry. Instead where they differed was over the meaning of “keep and bear Arms” and the significance of the first thirteen words of the amendment. The majority saw those words as “prefatory” and focused on what it called the “operative” language announcing a right. By contrast, Justice John Paul Stevens’s dissent treated the militia discussion as “preamble” shaping and constraining what came after.

Despite relying on similar sources—such as the drafting and ratification histories of the amendment, the history of contemporaneous state constitutional provisions, and existing practice at the time the amendment was ratified—the majority and the dissent reached divergent conclusions about the amendment’s original meaning. In particular, Justice Stephen Breyer’s dissent detailed various restrictions on firearms that existed during the colonial period and concluded, “Irrespective of what the Framers could have thought, we know what they did think”—that restrictions on firearms were consistent with the Second Amendment.

When Justice Scalia turned from abstract principle to actually resolving the case before him, he abandoned originalism in favor of the kind of contemporary understanding he so often decries. Why does the Second Amendment protect the ownership of handguns, a form of “Arms” quite different from the muskets and rifles owned by colonial Americans? Justice Scalia thought that it “border[ed] on the frivolous” to suggest that the amendment protected only 18th-century weapons: “We do not interpret constitutional rights that way.” Citing cases involving First Amendment protection of online speech and Fourth Amendment protection against the government’s use of thermal-imaging devices, Justice Scalia explained, the “Second Amendment extends, prima facie, to all instruments that constitute bearable arms, even those that were not in existence at the time of the founding.”

Justice Scalia’s reading is only plausible because the Court sees the words of the amendment as standing for a broader principle about the right to self-defense using available technology. But if “Arms” should be construed at a level of abstraction that takes into account contemporary understandings—and Justice Scalia found constitutional relevance in the fact that handguns are “overwhelmingly chosen by American society” today for purposes of self-defense—then why do originalists look to 18th- or 19th-century understandings to determine the scope of terms such as “liberty,” “cruel and unusual punishment,” or “equal protection of the laws”?

Moreover, modern practice also shaped the Court’s understanding of which “Arms” the Amendment protects. According to Heller, handguns are protected, but sawed-off shotguns and military-grade weapons such as machine guns are not. As Winkler points out, the Court could exclude these weapons as “dangerous and unusual” precisely because existing gun-control laws have effectively criminalized their possession. “Rather than defer to the original understanding, the majority opinion looks to contemporary government regulation,” Winkler writes. “This sounds a lot like a right evolving with the times—that is, a living Constitution.”

There also is little originalism in the Court’s treatment of the regulations themselves. Having announced an individual right to “keep and bear” handguns, the Court then indicated its receptivity to a broad range of government regulations, including laws “forbidding the carrying of firearms in sensitive places such as schools and government buildings” and blanket bans on gun possession by felons and mentally ill persons. That receptivity is inconsistent with the Court’s equation of the “right of the people” set forth in the Second Amendment with the rights protected by the First and Fourth Amendments. For example, the Court has repeatedly protected free speech inside schools and other government buildings, and mentally ill people retain protection against unreasonable searches and seizures.

Here, too, the explanation for the Court’s position lies not in the 18th or 19th centuries, but in the 21st. In Heller, the Court signaled its approval of these restrictions because, whether the justices admit it or not, they care about consequences. They engage in interest balancing: governments are entitled to conclude that the social costs of permitting weapons in schools or government buildings outweigh any individual right. Even after Heller, the Court has let stand lower-court decisions upholding restrictions on the right to carry concealed weapons outside the home. The difference on this point between the majority and Justice Breyer is not that one engages in interest balancing and the other does not. Rather it lies in Justice Breyer’s candor and the majority’s disingenuousness, and in how they weigh the competing considerations.

While Heller changed the doctrinal landscape, its effect on the scope of permissible legislation is fairly small. Standing alone, Heller held only that governments cannot enact absolute bans on handgun possession among law-abiding individuals for self-defense within their own homes. But that is not to say that the decision was insignificant, for by articulating a constitutional right, the Court can shift the nature of the political debate by reinforcing gun-control opponents’ claims that there is something constitutionally suspect about restrictions on weapons. And in that way, the justices may influence the future evolution of legal regulation just as they were themselves influenced by previous evolutions of political and popular understandings.