Heller was a 5-to-4 decision, and Justice John Paul Stevens, who wrote the principal dissenting opinion, indicated in a memoir published shortly before his death last month that Justice Antonin Scalia, the majority opinion’s author, had to compromise to hold his majority. His opinion deemed the right to keep a handgun at home for self-defense as the “core” Second Amendment right and continued: “It is not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose.” The court thus left undefined both what it was protecting beyond the “core” and how vigorously courts should scrutinize restrictions that extend out from the home or that deal with other kinds of firearms.

In his memoir, “The Making of a Justice,” Justice Stevens described his disappointment at failing to recruit Justice Anthony Kennedy to his side of the argument. His clear suggestion was that it was Justice Kennedy who extracted some of the limiting language as the price for signing the majority opinion. Now, of course, Justice Kennedy is gone. His successor, Justice Kavanaugh, based on the views he expressed while a federal appeals court judge, will have no such diffidence about endorsing a far-reaching Second Amendment.

But while the New York case, which does not yet have an argument date, emerged this spring as a significant test of the justices’ Second Amendment appetite, it has become in recent weeks something even more. On July 22, New York City filed with the Supreme Court a “suggestion of mootness” and a request to suspend the briefing schedule. The city explained that two interlocking developments had occurred: In the session just ended, the State Legislature had amended the handgun licensing statute to require localities to allow licensed handgun owners to transport their guns to second homes and target ranges outside the city; and the New York City Police Department, which supervises gun licensing, had amended the prior regulation to permit the same activities. The city argued that since the lawsuit had challenged only the second-home and shooting-range limitations, the plaintiffs now had everything they had asked for and there was nothing left for the Supreme Court to decide.

Ordinarily, the court readily grants a motion to declare a case moot; it did that last year after Congress passed a law that resolved a dispute between Microsoft and the federal government over a warrant for an overseas email account. Ordinarily, but not always. The Rifle & Pistol Association has fought back vigorously, arguing in a 33-page brief that “the city has not even tried to hide the fact that its paramount goal is to evade the prospect of a binding unfavorable decision from this court.” Further, the brief argues, the new regulation falls “far short” of satisfying the plaintiffs and is “plainly designed to provide the bare minimum of what the city believes will suffice to moot this case, and not an inch more.” It’s clear that the plaintiffs’ real argument is with the very idea of regulation: “The city manifestly has not altered its view that any possession of a handgun outside the home, even when the handgun is unloaded and stored away, is a privilege that the city can micromanage, rather than an individual right.”

Briefs have come in on both sides of this arcane argument. (The justices rejected the city’s request to suspend the briefing.) Moot for real or mootness as gamesmanship? Moot as in “nothing left to argue about ever again” or moot as an example of “voluntary cessation” that can be renounced at some future date? Last week, the justices took the unusual step of putting the mootness dispute on the agenda for discussion at their first closed-door conference of the new term, on Oct. 1.