N.Y. Est. Powers & Trusts Law § 7-1.16

§ 7-1.16 Revocation of lifetime trust by will\n A lifetime trust shall be irrevocable unless it expressly provides\nthat it is revocable. In addition to the method set forth in 7-1.17, a\nrevocable lifetime trust can be revoked or amended by an express\ndirection in the creator's will which specifically refers to such\nlifetime trust or a particular provision thereof.\n