In a 5–4 decision on the final day of the 2017–2018 term, the U.S. Supreme Court ruled that the First Amendment prohibits public-sector entities from collecting fees from nonunion members. This decision is seen as a significant blow to public-sector labor organizations nationwide, which rely on these “fair share” fee arrangements as a significant source of revenue.

But this decision will have an impact far beyond public employers. By weakening the ability of public-sector unions to raise funds, it could also signal an end to a lot of union-sponsored legislation at both the state and local levels.

These fair share ...