Nassau's Sheriff Officers Association has filed suit in federal court challenging a state control board's freeze on its contractual salary increases.
The correction officers' union is Nassau's last major union to challenge the year-long freeze imposed by the Nassau Interim Finance Authority, effective April 1.
The county's three police unions and the Civil Service Employees Association have already filed suit.
NIFA took control of the county's finances in January after calculating that Nassau's $2.6-billion budget contained a $176-million deficit. At the request of County Executive Edward Mangano, NIFA declared a fiscal crisis in March and froze salaries for an expected savings this year of $10 million.
The unions contend the freeze is illegal because it violates their due-process rights and the contracts clause of the U.S. Constitution. NIFA declined to comment on the lawsuit.