By Nate Raymond

BOSTON (Reuters) - A federal appeals court on Wednesday weighed whether the U.S. Constitution guarantees a right to carry guns in public for self-defense in a lawsuit challenging the firearm licensing policies of two Massachusetts municipalities including Boston.

The arguments before the 1st U.S. Circuit Court of Appeals in Boston marked the latest instance in which a federal appeals court has weighed the extent the Constitution's Second Amendment protects the right to carry firearms outside of a person's home.

The extent of the right to gun ownership is one of the most hotly contested debates in the United States, which has seen a steady stream of mass shootings in recent years.

Gun-rights activists hope that appellate court rulings prompt the U.S. Supreme Court to take up its first major gun rights case since 2010.

David Thompson, a lawyer for the gun-rights organization Commonwealth Second Amendment, in court argued Boston and Brookline had imposed an unconstitutional requirement that firearm license applicants to prove they had a specific reason to fear violence.

"I don't believe there's any historical law from the time of the founding that imposed on law-abiding citizens the need to prove to the government that they had some concern about their safety," he argued.

He cited a 2008 ruling in which the Supreme Court held the Second Amendment guaranteed a right to keep a handgun in one's home for self-defense.

But lawyers for Boston and Brookline urged the three-judge panel to affirm a ruling from December that held that the restrictions do not violate the right of citizens to bear arms under the Second Amendment.

They argued Thompson was wrong in contending the policies amounted to a flat ban on carrying handguns in public as a quarter of applicants had obtained unrestricted licenses, a fact U.S. Circuit Judge Bruce Selya noted.

"It provides open opportunities for people to be able to carry," Selya said.

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The arguments came after a different federal appeals court on Tuesday in a case involving Hawaii held the Second Amendment guarantees a right to carry a gun in public for self-defense, joining two other circuit courts that have ruled on the issue.

Three others have reached contrary conclusions, creating a split that could prompt the Supreme Court to intervene.

Republican President Donald Trump is seeking to fill a vacant Supreme Court seat and make the court more conservative, raising the prospect it may take up more gun-rights cases.





(Reporting by Nate Raymond in Boston; Editing by Lisa Shumaker)