Wis. Stat. § 702.103: Governing law.

Unless the terms of the instrument creating a power of appointment manifest a contrary intent, the creation, revocation, or amendment of a power of appointment is governed by the law of the donor’s domicile at the relevant time. The exercise, release, or disclaimer of a power of appointment, or the revocation or amendment of an exercise, release, or disclaimer of a power of appointment is governed by the law of the powerholder’s domicile at the relevant time.