Wis. Stat. § 757.45

It is unlawful for any person to divide with or receive from, or to agree to divide with or receive from, any attorney or group of attorneys, whether practicing in this state or elsewhere, either before or after action brought, any portion of any fee or compensation, charged or received by such attorney or any valuable consideration or reward, as an inducement for placing or in consideration of having placed, in the hands of such attorney, or in the hands of another person, a claim or demand of any kind for the purpose of collecting such claim, or bringing an action thereon, or of representing claimant in the pursuit of any civil remedy for the recovery thereof; but this section does not apply to an agreement between attorneys and counselors at law when associated in the conduct of legal matters to divide between themselves the compensation to be received. Any person violating this section shall be fined not to exceed $500 or imprisoned not to exceed 6 months.