Section 5-210
A guardian's authority and responsibility terminates upon the death, resignation, or removal of the guardian or upon the minor's death, adoption, marriage, or attainment of majority, but termination shall not affect the guardian's liability for prior acts or the obligation to account for funds and assets of the ward. Resignation of a guardian shall not terminate the guardianship until it has been approved by the court. A parental appointment under an informally probated will is voided if the will is later denied probate in a formal proceeding.