Minn. Stat. § 257B.07
Subd. 1. Prepetition.
Prior to a petition being filed under this chapter, the designator may revoke the appointment of a standby or temporary custodian by destruction of the designation and notification of the revocation to the standby or temporary custodian.
Subd. 2. Postpetition.
After a petition has been filed, the designator may revoke the designation of standby or temporary custodian by:
Subd. 3. Unwritten revocation.
An unwritten revocation of the designation may be considered by the court if it can be proven by clear and convincing evidence.