United States v. Harriss, 347 U.S. 612 (1954), was a U.S. Supreme Court case applied directly to the Regulation of Lobbying Act.

Lobbyists challenged the Regulation of Lobbying Act for being unconstitutionally vague and unclear.

The Court ruled that the act applies only to paid lobbyists who directly communicate with members of Congress on pending or proposed federal legislation.

In addition, the act covers only attempts to influence the passage or defeat of legislation in Congress, and excludes other congressional activities.

Further, the act applies to and restricts only individuals who spend at least half of their time lobbying.