The Justice Department is investigating "vague" standards Philadelphia police use to cancel and issue permits to carry legal firearms to determine if those practices are unconstitutional. 

“I have directed the Civil Rights Division, through our Second Amendment Section, to defend law-abiding citizens from local authorities who infringe the right to safely carry legal firearms," Assistant Attorney General Harmeet Dhillon of the Justice Department’s Civil Rights Division said in a statement. 

Supreme Court rulings have held that permitting officials may not base licensing decisions on personal discretion. The DOJ investigation is focused on allegations that the Philadelphia police are using those standards to limit gun owners' Second Amendment rights. 

“Law-abiding Americans, regardless of where they live, should not have to worry that their city will revoke their means of self-defense," Dhillon said. 

The investigation, the DOJ notes, is focused on the permitting system of the Philadelphia police and doesn't support any armed obstruction of federal or local law enforcement.