N.Y. RPP Law § 267

§ 267. Conveyances with power to revoke, determine or alter. A\nconveyance of, or charge on, an estate or interest in real property,\ncontaining a provision for the revocation, determination or alteration\nof the estate or interest, or any part thereof, at the will of the\ngrantor, is void, as against subsequent purchasers and incumbrancers,\nfrom the grantor, for a valuable consideration, of any estate or\ninterest so liable to be revoked or determined, although the same be not\nexpressly revoked, determined or altered by the grantor, by virtue of\nthe power reserved or expressed in the prior conveyance or charge. Where\na power to revoke a conveyance of real property or the rents and profits\nthereof, and to reconvey the same, is given to any person, other than\nthe grantor in such conveyance, and such person thereafter conveys the\nsame real property, rents or profits to a purchaser or incumbrancer for\na valuable consideration, such subsequent conveyance is valid, in the\nsame manner and to the same extent as if the power of revocation were\nrecited therein, and the intent to revoke the former conveyance\nexpressly declared. If a conveyance to a purchaser or incumbrancer,\nunder this section, be made before the person making it is entitled to\nexecute his power of revocation, it is nevertheless valid, from the time\nthe power of revocation actually vests in such person, in the same\nmanner, and to the same extent, as if then made.\n