WBRZ-TV reports the ordinance requires everyone in town, including drivers, to be off the streets after 11 p.m. or face a $500 fine and possibly 30 days in jail.
The organization filed the suit on behalf of Thomas Mead, of Clinton. It says Mead is often out at night and needs to know that he can come and go without risk of arrest.
Police Chief Frederick Dunn claims the measure has reduced crime in the town by 60 percent since it was enacted this past May. It was scheduled to end on July 31, but the town council extended it recently to Aug. 14.