In the United States v. American-Foreign Steamship Corp. et al., 1959, the Supreme Court ruled on a case involving maritime law and antitrust regulations. The defendants, several steamship companies operating between U.S ports and Australia/New Zealand, were accused of violating the Sherman Antitrust Act by conspiring to fix prices and divide markets among themselves for Pacific Coast outbound cargo trade. They argued that their actions were protected under Section 15 of the Shipping Act which allows common carriers to establish agreements regarding rates so long as they are filed with Federal Maritime Board (FMB). However, this filing had not been done at all times relevant to this suit. The court held that while such agreements may be exempt from antitrust laws if properly filed with FMB, failure to do so removes this exemption - thus making them subject to scrutiny under antitrust laws like any other business agreement or practice in commerce sector. Therefore, it was concluded that these shipping companies could indeed be prosecuted for violation of Sherman Antitrust Act due their failure in complying with requirements set forth by Shipping Act.

In the dissenting opinion for United States v. American-Foreign Steamship Corp., Justice Brennan argued that the majority's decision to allow a private shipping company to be exempt from antitrust laws was incorrect. He believed that this exemption should only apply when it is necessary for achieving a policy of the Shipping Act, which aims at maintaining an efficient and economic American merchant marine industry. However, he did not see any evidence suggesting such necessity in this case. Furthermore, he pointed out that Congress had explicitly stated its intention to preserve competition wherever possible within maritime industries while drafting these laws. Therefore, according to him, granting immunity from antitrust legislation without proper justification would undermine congressional intent and potentially harm competitive practices in maritime commerce.