In Gagnon v. United States, the Supreme Court dealt with a case involving customs duties on imported goods. The plaintiff, Gagnon, was an importer who claimed that he had been overcharged by the U.S government for import duties on sugar from Martinique and Guadeloupe. He argued that these islands were part of France according to international law and thus should be subject to lower duty rates under a treaty between the US and France. However, the court ruled against him stating that while they may technically belong to France in terms of sovereignty; economically and commercially they were separate entities as per their colonial status at that time which allowed them different trade regulations than mainland France itself. Therefore, it was within rights of Congress to impose higher tariffs on products coming from those colonies.

The Gagnon v. United States case does not have a recorded dissenting opinion available for summarization. This may be due to the fact that the decision was unanimous or no written dissent was provided by any of the justices.