The United States Civil Service Commission v. National Association of Letter Carriers case in 1972 revolved around the constitutionality of the Hatch Act, a federal law that prohibits civil service employees from participating in partisan political activities. The National Association of Letter Carriers and other unions challenged this act, arguing it violated their First Amendment rights to freedom of speech and association. However, the Supreme Court upheld the validity of the Hatch Act with a unanimous decision. They reasoned that limiting political activities for government workers was necessary to maintain an impartial and efficient public service system free from corruption or undue influence. The court also emphasized that these restrictions were not absolute; civil servants could still vote as they wished and express opinions on political subjects or candidates privately.

In the dissenting opinion for the United States Civil Service Commission v. National Association of Letter Carriers case, Justice Douglas argued that the Hatch Act, which restricts political activities of federal employees, was an infringement on First Amendment rights. He believed that it violated free speech and association by limiting political expression and involvement in partisan politics. Furthermore, he contended that there was no substantial evidence to suggest these restrictions were necessary to maintain a non-partisan civil service or prevent corruption within government ranks. Instead, he saw them as overly broad measures suppressing lawful political activity without sufficient justification.