N.Y. Public Service Law § 89-n

§ 89-n. Defense in case of excessive charges for water. If it be\nalleged and established in an action brought in any court for the\ncollection of any charge for water that a price has been demanded in\nexcess of that fixed by the commission or by statute in the municipality\nwherein the action arose, no recovery shall be had therein, but the fact\nthat such excessive charges have been made shall be a complete defense\nto such action.\n