On February 11, the Wisconsin legislature passed AB 223, which bans out-of-state circulators for candidate petitions and recall petitions. Wisconsin doesn’t have the initiative or referendum. In the Senate the vote was party-line, with all Democrats voting “no” and all Republicans voting “yes.” Wisconsin has a Democratic Governor, so it’s possible this bill will be vetoed.
Oddly the bill does not cover petitions to create a new party. That type of petition, which requires 10,000 signatures, is very seldom used. Generally minor parties become ballot-qualified by circulating a candidate petition for a statewide office and having that candidate poll at least 1% of the vote.
Wisconsin is in the Seventh Circuit. In 2000 the Seventh Circuit ruled that it is unconstitutional for a state to ban out-of-state circulators. Krislov v Rednour, 226 F.3d 851. That was an Illinois case. Illinois appealed to the U.S. Supreme Court, but that court refused to hear it.