Vị trí quan trọng của Pháp luật trong vụ kiện vũ khí của Tòa án Tối cao Thường được sử dụng như một biện pháp ngăn chặn

The federal law at the heart of a major Supreme Court case that could determine the scope of gun rights in the United States deals with one of the country’s most vexing problems. While the statute has not been used to prosecute a substantial number of people subject to domestic violence orders who are carrying guns, its greatest effect has been as a deterrent.

It is primarily used to stop domestic abusers facing restraining orders from getting guns. If someone is under such an order, that person’s name is entered into a database of people banned from buying firearms at gun stores — just like convicted felons. Over the past 25 years, people who tried to buy guns at licensed gun stores were rejected because of having active protection orders about 78,000 times, according to the F.B.I.

“We don’t do it for the prosecutions,” said Jennifer Becker, the director of the National Center on Gun Violence in Relationships at the Battered Women’s Justice Project. “It’s the background check system.”

Ms. Becker continued: “There have been so many cases where we have prevented a homicide because after she got the protection order and tried to leave, he went to buy a gun at a gun dealer. The background check system spotted the protection order. And it stopped the gun sale. This is huge.”

The New York Times found only 63 federal cases nationwide over the past five years of people being indicted on a charge of having a weapon while being under a domestic violence protection order. The defendant at the center of the case the court will hear on Tuesday, Zackey Rahimi, is one of them. In just 20 of the cases did prosecutors charge a person with only the crime of possessing a gun while having a protection order.

Still, the law can ensure that the person faces federal charges on top of local ones — most often they face other and often more serious charges. It can also guarantee that someone potentially dangerous is immediately detained.

For instance, John Allen Muhammad, the older of the two men who terrorized the Washington area with sniper killings in 2002, was originally arrested on the charge; his wife had a domestic-protection order against him when he was known to have a firearm.

But the Supreme Court’s landmark decision in June last year vastly expanded a person’s right to carry a gun in public and upended the standard for determining whether gun laws are constitutional. In his majority opinion, Justice Clarence Thomas said courts must look to early American history in judging restrictions on guns rights, and lawyers, in turn, started mounting a variety of challenges to gun laws, including the one prohibiting people subject to domestic abuse orders from having a firearm.

If the court overturns the federal law, the ruling is likely to reverberate across the country, legal experts say.

Currently, 32 states and the District of Columbia all have similar laws that prevent people with domestic violence protection orders from having guns, according to Everytown for Gun Safety. Some are more expansive than their federal counterpart, which does not apply to boyfriends or girlfriends who do not live with the victims. In Louisiana, for instance, the law protects dating partners. In several other states without laws, judges are given the discretion to remove guns when someone is granted a protection order.

A recent report from the RAND Corporation surveyed the available studies and found “moderate evidence” that those laws “reduce total and firearm-related intimate partner homicides.”

A decision by the court rejecting the law would most likely give rise to challenges to a parallel federal law whose primary effect is also as a deterrent. That law bans people with prior misdemeanor convictions for domestic violence from having a weapon; 31 states and the District of Columbia have similar laws, which would also be in jeopardy.

In the past 25 years, people who tried to get guns from licensed firearms stores were stopped because of having a prior misdemeanor conviction for domestic violence more than 191,000 times, according to the F.B.I.

The Times identified 328 people charged under this statute under the past five years. More than 100 of those cases were all in the northern district of Ohio, where officials have tried to use the statute much more aggressively.

Adam Liptak contributed reporting.