As recent events in Wisconsin have demonstrated, public‐sector unions are powerful political constituencies that can shape government to their ends. The Service Employees International Union, for example, the defendant in this case, has been ranked by OpenSecrets.org as the fifth biggest “heavy hitter” in federal politics in terms of campaign spending. In 2005, the SEIU initiated a mid‐year campaign against two California ballot measures, one that would cap state spending and another that would restrict the use of union dues for political purposes. In states such as California that do not have “right to work” laws, unions are allowed to take dues from non‐union workers to finance collective‐bargaining activities that, arguably, benefit all employees. Since 1977, however, unions have not been allowed to take dues from non‐union members to pay for pure political advocacy without adequate protections for possible dissenters. In order to distinguish political money from collective‐bargaining money, the Supreme Court requires that a “Hudson notice” be given to all non‐union workers. This notice gives non‐members the opportunity to challenge political expenditures. But when the SEIU began garnishing 25–33% more wages to fight the California ballot initiatives, it issued no new Hudson notice, effectively forcing 28,000 non‐member employees to finance its political speech. As Judge J. Clifford Wallace wrote in dissent from the Ninth Circuit’s ruling in favor of the SEIU, “it is undeniably unusual for a government agency to give a private entity the power, in essence, to tax government employees.” Now before the Supreme Court, Cato joined the Pacific Legal Foundation, the Center for Constitutional Jurisprudence, and the Mountain States Legal Foundation, on a brief supporting the non‐union workers and arguing that the Court should focus not on the extent of the burden Hudson places on unions (as the Ninth Circuit did) but on the paramount reasons why the notice requirements exist in the first place: to ensure that an individual’s right to speak or remain quiet receives the protection it deserves. As Judge Wallace put it, “the union has no legitimate interest … in collecting agency fees from nonmembers to fill its political war‐chest.” We also highlight the numerous unscrupulous tactics that unions have used over the years that violate the rights of dissenting workers—the same kind of rights that the Ninth Circuit treated with indifference. Finally, in light of the extreme political power that unions enjoy, the Court should find that the only way to adequately protect the rights of dissenting workers is to require that all non‐union members must “opt‐in” to any garnishment of wages for political purposes.