Wis. Stat. § 893.825: Statutory challenges.

(1) In an action in which a statute is alleged to be unconstitutional, or to be in violation of or preempted by federal law, or if the construction or validity of a statute is otherwise challenged, the attorney general shall be served with a copy of the proceeding and is entitled to be heard.

(2) In an action in which a statute is alleged to be unconstitutional, or to be in violation of or preempted by federal law, or if the construction or validity of a statute is otherwise challenged, the speaker of the assembly, the president of the senate, and the senate majority leader shall also be served with a copy of the proceeding and the assembly, the senate, and the joint committee on legislative organization are entitled to be heard.