N.Y. Estates, Powers & Trusts Law § 11-1.2
(b) Unless otherwise expressly provided by a will under which a disposition is made to or for the benefit of the surviving spouse of a decedent which qualifies for an estate tax marital deduction under any tax law of the state of New York or of the United States and the amount or size of such disposition is defined by the will in terms of the maximum marital deduction allowable under such tax law: