Massachusetts and New Hampshire are embroiled in a gun dispute that could extend beyond New England and eventually involve the U.S. Supreme Court.

The issue is the right to travel with guns between states with different firearm regulations. Massachusetts’ highest appeals court is considering the case of a New Hampshire man who had traveled to the state with his firearm without a license from the commonwealth. And in the gun owner’s defense, New Hampshire is calling for Massachusetts to end its strict licensing law for visitors.

States have wrestled with firearm restrictions in the two years since the Supreme Court ruled in New York State Rifle & Pistol Association Inc. v. Bruen that gun control laws must be consistent with the history and traditions at the nation’s founding to be constitutional.

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The issue of the right to travel with firearms will likely come before the Supreme Court, which has ruled on other gun control cases since its landmark 2022 ruling in Bruen, said Ilya Shapiro, director of constitutional studies at the Manhattan Institute.

“It is definitely something that has been litigated and will continue to be litigated,” Mr. Shapiro said.

The clash between New Hampshire and Massachusetts has garnered attention from pro-gun groups like the Second Amendment Foundation and the National Rifle Association, which filed a brief this month in support of the New Hampshire man fighting the commonwealth’s charges as the case pends before the Massachusetts Supreme Judicial Court during its 2024 session.

The pro-gun organizations argue that there is no historical tradition of a state licensing scheme for nonresidents.

“Historically, nonresidents traveling in a state were treated no worse than residents with regard to firearm carry. If they were treated differently under the law, it was generally to exempt travelers from carry restrictions — not to subject them to more onerous burdens than residents,” their filing read.

New Hampshire resident Dean F. Donnell traveled to Massachusetts in 2021 with a firearm. Massachusetts, which requires gun owners to acquire a temporary permit when visiting the commonwealth, charged Mr. Donnell with a felony for violating the law.

Lowell District Court Judge John Coffey dismissed the case in 2023, saying that “requiring non-residents to obtain licenses to carry firearms violates the Second Amendment because there is no historical analogue burdening the right to interstate travel.” Judge Coffey cited the Bruen decision in his ruling.

Prosecutors appealed Judge Coffey’s decision to the Massachusetts Supreme Judicial Court. The state attorneys said the judge’s reasoning invokes “novel but erroneous applications of Second Amendment constitutional law.”

“The motion judge erroneously ruled that out-of-state residents may not be prosecuted for unlawful possession of firearms in Massachusetts if they were legally entitled to possess those weapons in their home state,” the prosecutors’ filing read. “The judge’s rationale deprives the Commonwealth of its right and obligation to enforce its laws equally for all those who are within its borders.”

They said the decision was already stayed as the trial judge had applied the same reasoning in seven other cases.

But New Hampshire Attorney General John M. Formella announced Monday that New Hampshire residents’ frequent travel to Massachusetts suggests the commonwealth’s strict licensing law should be curtailed.

In his filing, Mr. Formella notes that a mall shares the border between the states and an individual with a gun in his or her car in the parking lot could violate the commonwealth’s requirements while abiding by New Hampshire’s.

“Given the frequent travel between New Hampshire and neighboring Massachusetts, the State of New Hampshire supports this ruling and argues that Granite Staters (or any non-Massachusetts residents) who are temporarily traveling to Massachusetts should not face potential felony convictions and imprisonment solely for lacking a Massachusetts gun license or permit,” Mr. Formella’s office said in a news release.

Mr. Formella said the brief — filed in support of Mr. Donnell and another New Hampshire man, Phillip Marquis — is crucial because it supports Second Amendment rights.

“By challenging Massachusetts’ restrictive firearm laws, we are affirming that constitutional freedoms should not be undermined by inconsistent and overly burdensome regulations,” Mr. Formella said. “This is all about ensuring that responsible gun owners can protect themselves without fear of unjust legal consequences when they cross state borders. Upholding these rights is essential for safeguarding personal safety and reinforcing the principle that the Constitution must be respected and upheld nationwide.”

A spokesperson from the district attorney’s office did not immediately return a request for comment.

In its 2022 Bruen decision, the high court in a 6-3 ruling divided along ideological lines said a New York gun licensing scheme was too restrictive since it required law-abiding individuals to show proper cause in order to obtain a permit and carry a firearm for self-defense. The court said that ran afoul of the Second Amendment.

Andrew Willinger, executive director of the Duke Center for Firearms Law, said he thought Judge Coffey’s reasoning in citing Bruen to dismiss charges against Mr. Donnell was in conflict with what the Supreme Court ruled, in that the justices did not strike down varying state licensing requirements. The court only said New York’s requirement to show proper cause ran afoul of the Constitution.

“The decision is difficult to square with the recognition in Bruen (and concurring opinions in that case) that states can continue to maintain different approaches for concealed carry licensing,” Mr. Willinger said in an email.