In the case of United States Postal Service v. National Association of Letter Carriers, AFL-CIO (1987), the Supreme Court ruled in favor of the U.S. Postal Service, upholding its decision to terminate an employee for misusing sick leave. The court found that arbitrators exceeded their powers by reinstating a postal worker who had been fired for abusing sick leave privileges and lying about it when questioned by his supervisors. The ruling stated that while labor agreements often give arbitrators broad authority to resolve disputes over contract interpretation or application, they do not have unlimited power to second-guess management decisions regarding discipline or discharge for just cause.

In the dissenting opinion for United States Postal Service v. National Association of Letter Carriers, AFL-CIO, Justice Blackmun argued that the majority's decision to uphold a ban on partisan political activities by postal workers was an overreach and violated First Amendment rights. He contended that there was no compelling government interest in maintaining such a broad prohibition against political activity, especially given its impact on free speech and association rights. Furthermore, he criticized the majority’s reliance on outdated precedents from an era when civil service protections were not as robust as they are today. In his view, modern safeguards against coercion and corruption made it unnecessary to restrict employees' political freedoms so severely.