We've seen Gov. Scott Walker's battle in Wisconsin and the Chicago Teachers Union strike next door. Now in Michigan comes another Midwestern political showdown that will carry enormous implications for the role of unions in American life.

As Shikha Dalmia explains, the Michigan Supreme Court recently approved the placement of a proposed constitutional amendment on the November ballot. If passed by voters, the so-called Protect Our Jobs amendment would give public-employee unions a potent new tool to challenge any laws—past, present, or future—that limit their benefits or collective-bargaining powers. It would also bar Michigan from becoming a right-to-work state in which mandatory union dues are not a condition of employment. The budget implications are dire.