By a premarital agreement executed in 1922 the wife of decedent waived all rights in his estate. The waiver was signed but not acknowledged. In August, 1930, decedent executed a will leaving $2,000 to his wife. In September, 1930, there went into effect an amendment of the Decedents\u27 Estate Law of New York, which gave to a widow an election to take under or against the will of her husband and provided that such election could be waived only by an instrument signed and acknowledged. The statute applied only to wills executed after September, 1930. The decedent executed a codicil to his will after 1930 and hence the will came within the provisions of the statute. Decedent\u27s executor claimed that so far as the statute invalidated the pre...