C.R.S. § 38-10-103: Conveyance determinable at will of grantor void.

Every conveyance or charge of or upon any estate or interest in lands containing any provision for the revocation, determination, or alteration of such estate or interest, or any part thereof, at the will of the grantor shall be void as against subsequent purchasers from such grantor, for a valuable consideration, of any estate or interest so liable to be revoked, determined, or altered by such grantor, by virtue of the power reserved or expressed in such prior conveyance or charge.