Wisconsin constitution
Article IV: legislative
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.

Structure Wisconsin constitution