A powerholder may revoke or amend an exercise of a power of appointment unless:
1. The terms of the instrument exercising the power of appointment expressly state that the exercise is irrevocable or unamendable;
2. The terms of the instrument creating the power of appointment expressly state that the exercise is irrevocable or unamendable; or
3. The property is subject to a present exercisable power of appointment that has been delivered to the permissible appointee in whose favor the power was exercised, regardless of whether such delivery was made outright, in trust or as custodial property pursuant to chapter 167 of NRS.