Wis. Stat. § 13.365: Intervention.

Pursuant to s. 803.09 (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:

(1) The committee on assembly organization may intervene at any time in the action on behalf of the assembly. The committee on assembly organization may obtain legal counsel other than from the department of justice, with the cost of representation paid from the appropriation under s. 20.765 (1) (a), to represent the assembly in any action in which the assembly intervenes.

(2) The committee on senate organization may intervene at any time in the action on behalf of the senate. The committee on senate organization may obtain legal counsel other than from the department of justice, with the cost of representation paid from the appropriation under s. 20.765 (1) (b), to represent the senate in any action in which the senate intervenes.

(3) The joint committee on legislative organization may intervene at any time in the action on behalf of the legislature. The joint committee on legislative organization may obtain legal counsel other than from the department of justice, with the cost of representation paid from the appropriation under s. 20.765 (1) (a) or (b), as determined by the cochairpersons, to represent the legislature in any action in which the joint committee on legislative organization intervenes.