Village managers don’t have a union. But when Thomas Barwin, Oak Park’s former manager, sued the village for allegedly refusing to permit him to purchase enough out-of-state credits to vest in the municipal pension plan, the 7th U.S. Circuit Court of Appeals concluded that labor law about arbitration involving “workplace practices” and “the law of the shop” supported its decision to reinstate his claim.Barwin alleged he was forced out as manager two-and-a-half years before his pension rights vested. He had two theories for …