The fate of Michigan's right-to-work law, that takes effect Thursday, is in the hands of four courts weighing a host of legal issues.
No judge is expected to rule this week on the measure that dealt a major defeat to organized labor in a bastion of the movement for generations.
But court challenges are likely to grow given a fight over lengthy public-sector labor contracts that critics say are an attempt to delay the law's impact.
Cases are pending in Ingham County, the state Court of Appeals, the Michigan Supreme Court and a federal court in Detroit.
Attempts to strike down a 2012 right-to-work law in Indiana have been unsuccessful. Organizers promise thousands of people across Michigan will rally against the law Thursday, wearing red as a show of solidarity.