A spokeswoman for Nielsen said the agency does not comment on pending litigation.

Shah said the defendants violated a federal law that requires government agencies to give prior notice and allow for public comment, adding that the rule is overly broad and has no end date.

In addition to the Canoe Cruisers, which was founded in 1956 and has about 250 members, the policy hampers paddling schools, summer camps for children, members of the U.S. Whitewater Team who are training for the Olympics and disabled veterans who paddle with Team River Runner, according to the lawsuit.

The security zone, known as “Seneca Lake,” is a calm stretch of river that is particularly useful for beginners, classes and river cleanup outings, the suit says.

“The beauty of the river is its privacy and solitude, and to have patrol boats on the river is so unsettling,” said Barbara Brown, an avid paddler since the late 1950s and head of the Canoe Cruisers.

The section is bordered on one end by a dam and Seneca Breaks rapids. It features two access points for paddlers on the Maryland shore: Riley’s Lock, where there is a county-run park, parking and the headquarters of a youth camp; and Violette’s Lock, which includes parking and a picnic area, the lawsuit says.