The tragedy happens—yesterday at a school in Oregon, and then as it will again—exactly as predicted, and uniquely here. It hardly seems worth the energy to once again make the same essential point that the President—his growing exasperation and disbelief moving, if not effective, as he serves as national mourner—has now made again: we know how to fix this. Gun control ends gun violence as surely an antibiotics end bacterial infections, as surely as vaccines end childhood measles—not perfectly and in every case, but overwhelmingly and everywhere that it’s been taken seriously and tried at length. These lives can be saved. Kids continue to die en masse because one political party won’t allow that to change, and the party won’t allow it to change because of the irrational and often paranoid fixations that make the massacre of students and children an acceptable cost of fetishizing guns.

In the course of today’s conversation, two issues may come up, treated in what is now called a trolling tone—pretending to show concern but actually standing in the way of real argument. One is the issue of mental health and this particular killer’s apparent religious bigotry. Everyone crazy enough to pick up a gun and kill many people is crazy enough to have an ideology to attach to the act. The point—the only point—is that, everywhere else, that person rants in isolation or on his keyboard; only in America do we cheerfully supply him with military-style weapons to express his rage. As the otherwise reliably Republican (but still Canadian-raised) David Frum wisely writes: “Every mass shooter has his own hateful motive. They all use the same tool.”

More standard, and seemingly more significant, is the claim—often made by those who say they recognize the tragedy of mass shootings and pretend, at least, that they would like to see gun sanity reign in America—that the Second Amendment acts as a barrier to anything like the gun laws, passed after mass shootings, that have saved so many lives in Canada and Australia. Like it or not, according to this argument, the Constitution limits our ability to control the number and kinds of guns in private hands. Even the great Jim Jeffries, in his memorable standup on American madness, says, “Why can’t you change the Second Amendment? It’s an amendment!”—as though further amending it were necessary to escape it.

In point of historical and constitutional fact, nothing could be further from the truth: the only amendment necessary for gun legislation, on the local or national level, is the Second Amendment itself, properly understood, as it was for two hundred years in its plain original sense. This sense can be summed up in a sentence: if the Founders hadn’t wanted guns to be regulated, and thoroughly, they would not have put the phrase “well regulated” in the amendment. (A quick thought experiment: What if those words were not in the preamble to the amendment and a gun-sanity group wanted to insert them? Would the National Rifle Association be for or against this change? It’s obvious, isn’t it?)

The confusion is contemporary. (And, let us hope, temporary.) It rises from the younger-than-springtime decision D.C. v. Heller_,_ from 2008, when Justice Antonin Scalia, writing for a 5–4 majority, insisted that, whether he wanted it to or not, the Second Amendment protected an individual right to own a weapon. (A certain disingenuous show of disinterestedness is typical of his opinions.)

This was an astounding constitutional reading, or misreading, as original as Citizens United, and as idiosyncratic as the reasoning in Bush v. Gore, which found a conclusive principle designed to be instantly discarded—or, for that matter, as the readiness among the court’s right wing to overturn a health-care law passed by a supermajority of the legislature over a typo. Anyone who wants to both grasp that decision’s radicalism and get a calm, instructive view of what the Second Amendment does say, and was intended to say, and was always before been understood to say, should read Justice John Paul Stevens’s brilliant, persuasive dissent in that case. Every person who despairs of the sanity of the country should read it, at least once, not just for its calm and irrefutable case-making but as a reminder of what sanity sounds like.

Stevens, a Republican judge appointed by a Republican President, brilliantly analyzes the history of the amendment, making it plain that for Scalia, et al., to arrive at their view, they have to reference not the deliberations that produced the amendment but, rather, bring in British common law and lean on interpretations that arose long after the amendment was passed. Both “keep arms” and “bear arms,” he demonstrates, were, in the writers’ day, military terms used in military contexts. (Gary Wills has usefully illuminated this truth in the New York Review of Books.) The intent of the Second Amendment, Stevens explains, was obviously to secure “to the people a right to use and possess arms in conjunction with service in a well-regulated militia.” The one seemingly sound argument in the Scalia decision—that “the people” in the Second Amendment ought to be the same “people” referenced in the other amendments, that is, everybody—is exactly the interpretation that the preamble was meant to guard against.

Stevens’s dissent should be read in full, but his conclusion in particular is clear and ringing:

The right the Court announces [in Heller] was not “enshrined” in the Second Amendment by the Framers; it is the product of today’s law-changing decision. . . . Until today, it has been understood that legislatures may regulate the civilian use and misuse of firearms so long as they do not interfere with the preservation of a well-regulated militia. The Court’s announcement of a new constitutional right to own and use firearms for private purposes upsets that settled understanding . . .

Justice Stevens and his colleagues were not saying, a mere seven years ago, that the gun-control legislation in dispute in Heller alone was constitutional within the confines of the Second Amendment. They were asserting that essentially every kind of legislation concerning guns in the hands of individuals was compatible with the Second Amendment—indeed, that regulating guns in individual hands was one of the purposes for which the amendment was offered.

So there is no need to amend the Constitution, or to alter the historical understanding of what the Second Amendment meant. No new reasoning or tortured rereading is needed to reconcile the Constitution with common sense. All that is necessary for sanity to rule again, on the question of guns, is to restore the amendment to its commonly understood meaning as it was articulated by this wise Republican judge a scant few years ago. And all you need for that is one saner and, in the true sense, conservative Supreme Court vote. One Presidential election could make that happen.