In McAllister v. United States, the Supreme Court ruled on a case involving maritime law and personal injury claims. The petitioner, Captain McAllister, was injured while working aboard a vessel owned by the U.S government and sought compensation under the Jones Act which provides for damages to seamen injured in their employment due to negligence of their employer or co-workers. However, he had previously received an award from the Federal Employees' Compensation Commission (FECC) for his injuries. The issue before the court was whether acceptance of this award barred him from pursuing further claims under other federal statutes like Jones Act. The Supreme Court held that accepting compensation from FECC did not preclude additional recovery under different legislation unless expressly stated by Congress - which it wasn't in this instance. Therefore, Captain McAllister could pursue his claim under Jones Act despite having already received some compensation through FECC.

In the dissenting opinion for McAllister v. United States, Justice Robert H. Jackson disagreed with the majority's decision to uphold a conviction based on evidence obtained through wiretapping by federal agents without a warrant. He argued that this violated the Fourth Amendment protection against unreasonable searches and seizures as well as Fifth Amendment protections against self-incrimination. Jackson contended that allowing such practices would set a dangerous precedent where law enforcement could invade personal privacy without any legal constraints or oversight, leading to potential abuses of power and violations of civil liberties. He also expressed concern about how this ruling might affect future cases involving similar issues, arguing it could undermine public trust in law enforcement and judicial fairness if people believed their private communications were not safe from unwarranted government intrusion.