A United Kingdom citizen who is a legal permanent resident of the United States alleges in a lawsuit that the Honolulu Police Department discriminates against non-U.S. citizens by making it difficult for them to obtain firearm permits.

Hawaii has some of the strongest gun laws in the nation. Hawaii is the only state that requires firearms to be registered at a statewide level, which is done through county police departments. Hawaii’s permit allows someone to purchase a firearm, transport it to limited places such as a shooting range or gunsmith, or use it for hunting.

Hawaii only granted permits to U.S. citizens until a federal judge in Honolulu last year ruled that’s unconstitutional.

The department is trying to get around that ruling by verbally requiring those with green cards to obtain additional clearance from their countries of citizenship, said the lawsuit filed last week in federal court in Honolulu.

Honolulu resident Andrew Namiki Roberts, who was born in England, was given a permit to acquire rifles and shotguns, which must first be obtained before purchasing one. He then took a firearms safety course, which is required to obtain a permit for a handgun, according to his lawsuit. But when he tried to get a handgun permit, he was told his background check was deemed incomplete and that he needed a letter from the British consulate clearing his background.

His lawyer, Richard Holcomb, said the department couldn’t produce written policy about requiring such documentation, but even if it could, it’s an unfair requirement. “They can’t discriminate against permanent resident aliens,” he said.

The department won’t comment on pending litigation, police spokeswoman Michelle Yu said.

The lawsuit notes that Hawaii law says if the permit applicant is not a U.S. citizen and is eligible to acquire a firearm, an inquiry on the applicant will be made using the National Instant Criminal Background Check System and the Immigration and Customs Enforcement databases.

The department also revoked his previously issued permit that allowed him to purchase a shotgun and then seized the weapon he bought from Sports Authority, the lawsuit said.

Requiring Roberts to get additional documentation from England is like requiring U.S. citizens to obtain clearances from countries they’ve lived in previously, Holcomb said.

“Mr. Roberts has the constitutional right to keep and possess firearms in his home for the purpose of self-defense,” his lawsuit said.