Democratic lawmakers in Nassau County, N.Y., have sued to end a program created last year by Executive Bruce Blakeman, a Republican, that enlisted armed citizens to volunteer as “special deputies” whom he would activate in case of emergency.

The lawsuit called the program an illegal and secretive militia that “represents a substantial and ongoing waste of public funds” in the county, which is just east of New York City.

The suit was filed in State Supreme Court in Mineola on Tuesday by two county legislators, Debra Mulé and Scott Davis.

It named Mr. Blakeman and his administration, along with the sheriff, Anthony LaRocco, and charged that Mr. Blakeman had created the program without the County Legislature’s authorization.

Blakeman administration officials were trying to “shroud their illegal program in secrecy” by illegally denying legislators’ Freedom of Information Act requests for details, the suit said.

“Authorizing minimally trained private citizens to wield force on behalf of the government — and during an emergency no less — poses clear and obvious safety risks,” it said.