Wis. Stat. § 618.34

Every nondomestic mutual insurer authorized in this state shall, immediately after making an assessment upon any of its members in this state, notify the commissioner thereof with a statement of the condition of the insurer, setting forth the facts showing the necessity for the assessment. No such insurer may make or increase any assessment because of its inability to collect assessments from its members in other states in which its policies were written in violation of law.