Wisconsin Constitution Art. IV § 13. Ineligibility of federal officers

Section 13. No person being a member of congress, or holding any military or civil office under the United States, shall be eligible to a seat in the legislature; and if any person shall, after his election as a member of the legislature, be elected to congress, or be appointed to any office, civil or military, under the government of the United States, his acceptance thereof shall vacate his seat. This restriction shall not prohibit a legislator from accepting short periods of active duty as a member of the reserve or from serving in the armed forces during any emergency declared by the executive.