A donor may revoke or amend a power of appointment only to the extent that: (1) the instrument creating the power is revocable by the donor; or (2) the donor reserves a power of revocation or amendment in the instrument creating the power of appointment.
Power To Revoke Or Amend
Mont. Code Ann. § 72-7-206, under Creation, Revocation, and Amendment of Power of Appointment.
Mont. Code Ann. § 72-7-206