The Matthew Addy Company v. United States case in 1923 revolved around the interpretation of a tariff act. The plaintiff, Matthew Addy Company, imported iron ore into the U.S and was charged with duties under paragraph 122 of the Tariff Act of October 3rd, 1913. However, they argued that their imports should have been free from duty as per paragraph 123 which exempted ores used for fertilizing purposes from taxation. The Supreme Court ruled against them stating that despite some portion of their import being usable as fertilizer due to its phosphorus content; it was primarily an iron ore and thus subject to tax under Paragraph 122. This decision upheld previous rulings by lower courts including Customs Court and Board General Appraisers who had also classified these imports as dutiable iron ores rather than non-dutiable fertilizers.

In the dissenting opinion for Matthew Addy Company v. United States, Justice McReynolds disagreed with the majority's interpretation of "vessel" under Section 3 of the Rivers and Harbors Act. He argued that a broader definition was intended by Congress to include all types of watercrafts, including floating platforms like those used by Matthew Addy Company. The justice believed that such structures could potentially obstruct navigation just as much as traditional vessels if left unregulated. Therefore, he contended that they should be subject to penalties under the Act when causing obstruction without necessary permits from authorities in charge of waterways management. This would ensure protection against any potential interference with navigable capacity of rivers and harbors across America.