Intervention
Wis. Stat. § 803.09
in effect(1) Upon timely motion anyone shall be permitted to intervene in an action when the movant claims an interest relating to the property or transaction which is the subject of the action and the movant is so situated that the disposition of the action may as a practical matter impair or impede the movant’s ability to protect that interest, unless the movant’s interest is adequately represented by existing parties.
(2) Upon timely motion anyone may be permitted to intervene in an action when a movant’s claim or defense and the main action have a question of law or fact in common. When a party to an action relies for ground of claim or defense upon any statute or executive order or rule administered by a federal or state governmental officer or agency or upon any regulation, order, rule, requirement or agreement issued or made pursuant to the statute or executive order, the officer or agency upon timely motion may be permitted to intervene in the action. In exercising its discretion the court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties.
(2m) When a party to an action challenges in state or federal court the constitutionality of a statute, facially or as applied, challenges a statute as violating or preempted by federal law, or otherwise challenges the construction or validity of a statute, as part of a claim or affirmative defense, the assembly, the senate, and the legislature may intervene as set forth under s. 13.365 at any time in the action as a matter of right by serving a motion upon the parties as provided in s. 801.14.
(3) A person desiring to intervene shall serve a motion to intervene upon the parties as provided in s. 801.14. The motion shall state the grounds therefor and shall be accompanied by a pleading setting forth the claim or defense for which intervention is sought. The same procedure shall be followed when a statute gives a right to intervene.
Source: WI Statutes (Official Site)URL: https://docs.legis.wisconsin.gov/document/statutes/803.09Fetched: 10/7/2026