The Private Express Statutes (PES) codified the postal monopoly of the United States Postal Service. A provision of the Private Express Statutes (PES) authorizes the Postal Service to suspend PES restrictions upon any mail route where the public interest so requires. The Postal Service suspended PES restrictions for international remailings. The American Postal Workers Union, AFL-CIO, and the National Association of Letter Carriers, AFL-CIO (Unions) (plaintiffs) challenged the international remailing regulation in federal court, pursuant to the judicial review provisions of the § 702 of the Administrative Procedure Act (APA). The United States Postal Service and Air Courier Conference of America (defendants) opposed the lawsuit on the ground that the plaintiffs lacked standing to bring their claim. The Unions took the position that they had standing to sue because the Postal Service’s suspension of the PES restrictions had adverse effects on their employment opportunities. The district court and court of appeals found that the Unions had standing. The United States Supreme Court granted certiorari.