Wisconsin Statutes

Wis. Stat. § 803.09 (2026)

Intervention

✓ current as of July 2026

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803.09803.09 Intervention.

803.09(1)(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.

803.09(2)(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.

803.09(2m)(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.

803.09(3)(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.

803.09 HistoryHistory: Sup. Ct. Order, 67 Wis. 2d 585, 650 (1975); 1975 c. 218; 2007 a. 20; 2015 a. 55; 2017 a. 369.

803.09 AnnotationA postjudgment applicant for leave to intervene must show sufficient reason for having waited. Sewerage Commission of Milwaukee v. DNR, 104 Wis. 2d 182, 311 N.W.2d 677 (Ct. App. 1981).

803.09 AnnotationIntervenors in an action cannot continue their claim once the original action is dismissed. Intervention will not be permitted to breathe life into a nonexistent lawsuit. Fox v. DHSS, 112 Wis. 2d 514, 334 N.W.2d 532 (1983).

803.09 AnnotationA newspaper could intervene to protect the right to examine a sealed court file. State ex rel. Bilder v. Township of Delavan, 112 Wis. 2d 539, 334 N.W.2d 252 (1983).

803.09 AnnotationA newspaper’s postjudgment motion to intervene to open sealed court records was timely and proper. C.L. v. Edson, 140 Wis. 2d 168, 409 N.W.2d 417 (Ct. App. 1987).

803.09 AnnotationMotions to intervene are evaluated practically, and not technically, with an eye toward disposing of lawsuits by involving as many apparently concerned persons as is compatible with efficiency and due process. There is no requirement that the intervenor’s interest be judicially enforceable in a separate proceeding. Wolff v. Town of Jamestown, 229 Wis. 2d 738, 601 N.W.2d 301 (Ct. App. 1999), 98-2974.

803.09 AnnotationAfter intervention, an intervenor’s status is the same as all other parties. Once a party intervenes, all claims and defenses against it may be asserted. Kohler Co. v. Sogen International Fund, Inc., 2000 WI App 60, 233 Wis. 2d 592, 608 N.W.2d 746, 99-0960.

803.09 AnnotationA non-party to a circuit court action may intervene in an appeal brought by another party, even after the time for filing a notice of appeal has passed. City of Madison v. WERC, 2000 WI 39, 234 Wis. 2d 550, 610 N.W.2d 94, 99-0500.

803.09 AnnotationIn order to prevail, a prospective intervenor must demonstrate that: 1) the movant claims an interest relating to the property or transaction subject of the action; 2) the disposition of the action may as a practical matter impair or impede the proposed intervenor’s ability to protect that interest; 3) the movant’s interest will not be adequately represented by existing parties to the action; and 4) the motion to intervene was made in a timely fashion. Motions to intervene must be evaluated with an eye toward disposing of lawsuits by involving as many apparently concerned persons as is compatible with efficiency and due process. M&I Marshall & Ilsley Bank v. Urquhart Cos., 2005 WI App 225, 287 Wis. 2d 623, 706 N.W.2d 335, 04-2743.

803.09 AnnotationTimeliness is not defined by statute, and there is no precise formula to determine whether a motion to intervene is timely. The question of timeliness is a determination necessarily left to the discretion of the circuit court and turns on whether, under all the circumstances, a proposed intervenor acted promptly and whether intervention will prejudice the original parties. Postjudgment motions for intervention will be granted only upon a strong showing of justification for failure to request intervention sooner. Olivarez v. Unitrin Property & Casualty Insurance Co., 2006 WI App 189, 296 Wis. 2d 337, 723 N.W.2d 131, 05-2471.

803.09 AnnotationIntervention by the legislature in a case with policy or budgetary ramifications when the executive branch, through the attorney general, fulfills its traditional role defending legislation before the court is not required. Legislators may often have a preference for how the judicial branch should interpret a statute, but such mere preferences do not constitute sufficiently related or potentially impaired interests within the meaning of sub. (1). Helgeland v. Wisconsin Municipalities, 2006 WI App 216, 296 Wis. 2d 880, 724 N.W.2d 208, 05-2540.

803.09 AnnotationAffirmed on other grounds. 2008 WI 9, 307 Wis. 2d 1, 745 N.W.2d 1, 05-2540.

803.09 AnnotationIn the context of sub. (2), “defense” conveys that the person seeking to intervene, although not named as a defendant, could be a defendant to a claim in the main action or a defendant to a similar or related claim. Sub. (3) supports this construction of “defense,”conveying that the “claim” or “defense” is more than arguments or issues a non-party wishes to address and is the type of matter presented in a pleading—either allegations that show why a party is entitled to the relief sought on a claim or allegations that show why a party proceeded against is entitled to prevail against the claim. Helgeland v. Wisconsin Municipalities, 2006 WI App 216, 296 Wis. 2d 880, 724 N.W.2d 208, 05-2540.

803.09 AnnotationAffirmed on other grounds. 2008 WI 9, 307 Wis. 2d 1, 745 N.W.2d 1, 05-2540.

803.09 AnnotationCourts have no precise formula for determining whether a potential intervenor meets the requirements of sub. (1) The analysis is holistic, flexible, and highly fact-specific. Sub. (1) attempts to strike a balance between two conflicting public policies: that the original parties to a lawsuit should be allowed to conduct and conclude their own lawsuit and that persons should be allowed to join a lawsuit in the interest of the speedy and economical resolution of controversies. Despite its nomenclature, intervention “as of right” usually turns on judgment calls and fact assessments that a reviewing court is unlikely to disturb except for clear mistakes. Helgeland v. Wisconsin Municipalities, 2008 WI 9, 307 Wis. 2d 1, 745 N.W.2d 1, 05-2540.

803.09 AnnotationIf a person has no right of intervention under sub. (1), the courts have no duty to join that person sua sponte as a necessary party under s. 803.03 (1) (b) 1. Whether a movant is a necessary party under s. 803.03 (1) (b) 1. is in all significant respects the same inquiry under sub. (1) as to whether a movant is entitled to intervene in an action as a matter of right, including the factor of whether the interest of the movant is adequately represented by existing parties. A movant who fails to meet that requirement for intervention as of right may not force its way into the action by arguing that the court must join the movant, sua sponte, as a necessary party under s. 803.03 (1) (b) 1. Helgeland v. Wisconsin Municipalities, 2008 WI 9, 307 Wis. 2d 1, 745 N.W.2d 1, 05-2540.

803.09 AnnotationCertain institutional interests of the legislature were sufficient to defeat a facial challenge to the provisions of this section authorizing legislative intervention in certain cases and those requiring legislative consent to defend and prosecute certain cases. Service Employees International Union (SEIU), Local 1 v. Vos, 2020 WI 67, 393 Wis. 2d 38, 946 N.W.2d 35, 19-0614.

803.09 AnnotationWhen the prerequisites in sub. (2m) are met, Wisconsin law gives the legislature, if it chooses to intervene, the power to represent the State of Wisconsin’s interest in the validity of its laws. Democratic National Committee v. Bostelmann, 2020 WI 80, 394 Wis. 2d 33, 949 N.W.2d 423, 20-1634.

803.09 AnnotationPermissive intervention, unlike intervention as a matter of right, requires only that a movant be a proper party, not a necessary party. While a court must consider three factors under sub. (2) in determining whether the movant is eligible to be considered for permissive intervention, the court, in exercising its discretion, need not permit the movant to intervene simply because the movant meets each of these factors. Braun v. Vote.org, 2024 WI App 42, 413 Wis. 2d 88, 11 N.W.3d 106, 23-0076.

803.09 AnnotationThe language of sub. (2m) implies that intervention should be automatic, without any input from the trial court, as long as the conditions for authorization under s. 13.365 are met. The right to intervene in a federal lawsuit is a purely procedural right, and, even in a diversity suit, it is the Federal Rules of Civil Procedure (FRCP) rather than state law that dictate the procedures, including who may intervene, to be followed. Sub. (2m) cannot supplant the FRCP and make intervention automatic. Planned Parenthood of Wisconsin, Inc. v. Kaul, 942 F.3d 793 (2019). But see Berger v. North Carolina State Conference of the NAACP, 597 U.S. 179, 142 S. Ct. 2191, 213 L. Ed. 2d 517 (2022).

Notes of Decisions

Cited in 85 cases (11 in the last 5 years), 1979–2025 · leading case: Helgeland v. Wisconsin Municipalities, 2008 WI 9 (Wis. 2008).

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Helgeland v. Wisconsin Municipalities, 2008 WI 9 (Wis. 2008). · cites it 194× “The Municipalities Do Not Have the Right to Intervene: Wis. Stat. § 803.09 (1): ¶¶ 35-120 A. Motion to Intervene is Timely: ¶ 42 B.”

Helgeland v. Wisconsin Municipalities, 2006 WI App 216 (Wis. Ct. App. 2006). · cites it 124× “§ 803.09, the then and present intervention statute.”

Wolff v. Town of Jamestown, 601 N.W.2d 301 (Wis. Ct. App. 1999). · cites it 21× “We conclude that the Town meets the requirements of § 803.09(1), Stats., and that it is thus entitled to intervene as of right in the Wolffs' action.”

Dairyland Greyhound Park, Inc. v. McCallum, 2002 WI App 259 (Wis. Ct. App. 2002). · cites it 10× “03(l)(b), 1 (whether a person who "claims an interest relating to the subject of the action.”

Doyle v. Engelke, 580 N.W.2d 245 (Wis. 1998). · cites it 8× “Paul intervened as a defendant pursuant to Wis. Stat. § 803.09 (1993-94). [2] St. Paul then filed a motion for summary judgment asking the circuit court to determine that pursuant to the terms of its Policy with WVCY, St.”

Town of Mentor v. State, 2021 WI App 85 (Wis. Ct. App. 2021). · cites it 12× “§ 803.09(1). Specifically, the Town fails to show that Montgomery’s placement in the Town may as a practical matter impair its ability to protect its only asserted interest in this case.”

Sewerage Comm'n of the City of Milwaukee v. State Dep't of Nat. Resources, 311 N.W.2d 677 (Wis. Ct. App. 1981). · cites it 19× “) Thus, whether intervention is a matter of right or only permissive, the application to intervene must be "timely." No statutory definition exists of "timely.”

Fontana Builders, Inc. v. Assurance Co. of Am., 2016 WI 52 (Wis. 2016). · cites it 4× “¶31 After the case returned to the Walworth County Circuit Court, AnchorBank filed a motion to intervene under Wis. Stat. § 803.09 (1). AnchorBank asserted an interest in any insurance proceeds due from Assurance in light of a foreclosure default judgment for $1,135,332.”

Baumeister v. Automated Prods., Inc., 2004 WI 148 (Wis. 2004). · cites it 4× “Baumeister and Brown moved to intervene pursuant to Wis. Stat. § 803.09 (1). On August 14, 2000, the circuit court issued an order permitting intervention.”

Armada Broad., Inc. v. Stirn, 516 N.W.2d 357 (Wis. 1994). · cites it 8× “In interpreting Rule 24(a)(2) of the Federal Rules of Civil Procedure upon which sec. 803.09, Stats., was based, see Bilder, 112 Wis.”

Steven v. v. Kelley H., 2004 WI 47 (Wis. 2004). · cites it 2× “2d at 143-44 , (citing the general rule that the civil procedure code governs Chapter 48 proceedings but concluding that the general intervention statute, Wis. Stat. § 803.09 , conflicts with the exclusive procedure in Wis.”

Roth v. LaFarge Sch. Dist. Bd. of Canvassers, 2001 WI App 221 (Wis. Ct. App. 2001). · cites it 8× “The supreme court recently set forth the requirements for intervention as a matter of right under Wis. Stat. § 803.09 (1): (1) the motion to intervene must be timely; (2) the movant must claim an interest in the subject of the action; (3) the outcome may, as a practical matter,…”

Show all 85 citing cases →

— Wis. Stat. § 803.09(1) — 27 cases

Helgeland v. Wisconsin Municipalities, 2006 WI App 216 (Wis. Ct. App. 2006). “§ 803.09, the then and present intervention statute.”

Wolff v. Town of Jamestown, 601 N.W.2d 301 (Wis. Ct. App. 1999). “We conclude that the Town meets the requirements of § 803.09(1), Stats., and that it is thus entitled to intervene as of right in the Wolffs' action.”

Helgeland v. Wisconsin Municipalities, 2008 WI 9 (Wis. 2008). “The Municipalities Do Not Have the Right to Intervene: Wis. Stat. § 803.09 (1): ¶¶ 35-120 A. Motion to Intervene is Timely: ¶ 42 B.”

Town of Mentor v. State, 2021 WI App 85 (Wis. Ct. App. 2021). “§ 803.09(1). Specifically, the Town fails to show that Montgomery’s placement in the Town may as a practical matter impair its ability to protect its only asserted interest in this case.”

Armada Broad., Inc. v. Stirn, 516 N.W.2d 357 (Wis. 1994). “In interpreting Rule 24(a)(2) of the Federal Rules of Civil Procedure upon which sec. 803.09, Stats., was based, see Bilder, 112 Wis.”

— Wis. Stat. § 803.09(2) — 16 cases

Helgeland v. Wisconsin Municipalities, 2006 WI App 216 (Wis. Ct. App. 2006). “§ 803.09, the then and present intervention statute.”

State Ex Rel. Jones v. Gerhardstein, 416 N.W.2d 883 (Wis. 1987).

Sewerage Comm'n of the City of Milwaukee v. State Dep't of Nat. Resources, 311 N.W.2d 677 (Wis. Ct. App. 1981). “) Thus, whether intervention is a matter of right or only permissive, the application to intervene must be "timely." No statutory definition exists of "timely.”

State Ex Rel. Jones v. Gerhardstein, 400 N.W.2d 1 (Wis. Ct. App. 1986).

— Wis. Stat. § 803.09(2m) — 5 cases

Savannah Wren v. Columbia St. Mary's Hosp. Milwaukee, Inc (Wis. Ct. App. 2025).

Disability Rights Wisconsin v. Wisconsin Elections Comm'n (Wis. Ct. App. 2025).

Liebert, Susan v. Wisconsin Elections Comm'n (W.D. Wis. 2023).

Rise, Inc. v. Wisconsin Elections Comm'n (Wis. Ct. App. 2023).

Josh Kaul v. Wisconsin State Legislature (Wis. Ct. App. 2024).

— Wis. Stat. § 803.09(3) — 2 cases

Helgeland v. Wisconsin Municipalities, 2006 WI App 216 (Wis. Ct. App. 2006). “§ 803.09, the then and present intervention statute.”

Wengerd v. Rinehart, 338 N.W.2d 861 (Wis. Ct. App. 1983).

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