Mont. Code Ann. § 72-2-826
72-2-826 Disclaimer by appointee, object, or taker in default of exercise of power of appointment
72-2-826 . Disclaimer by appointee, object, or taker in default of exercise of power of appointment. (1) A disclaimer of an interest in property by an appointee of a power of appointment takes effect as of the time the instrument by which the holder exercises the power becomes irrevocable.
(2) A disclaimer of an interest in property by an object or taker in default of an exercise of a power of appointment takes effect as of the time the instrument creating the power becomes irrevocable.