In United States v. Holliday, the Supreme Court of the United States considered a case involving an alleged violation of the Neutrality Act by John W. Holliday and two other individuals who had been indicted for conspiring to fit out a vessel with intent to cruise against Spanish vessels in 1864. The defendants argued that they were not guilty because their actions did not constitute warlike operations or hostile acts as defined by Congress under the Neutrality Act. The Supreme Court disagreed, finding that fitting out a vessel with intent to cruise against another nation's ships was sufficient evidence of hostility and thus constituted an offense under the law. Ultimately, it held that such activity was prohibited by Congress and could be punished accordingly, affirming its conviction on all counts.

In United States v. Holliday, the Supreme Court was asked to decide whether a defendant could be convicted of manslaughter if he had acted in self-defense but with excessive force. The majority opinion held that such an act constituted manslaughter and affirmed the conviction of the defendant. However, Justice Field dissented from this decision and argued that it should not be considered manslaughter since there was no criminal intent on behalf of the defendant when they acted in self-defense. He reasoned that any person who acts out of fear or necessity for their own safety should not be found guilty as long as they do not use more force than is necessary to protect themselves against harm or death. Furthermore, Field argued that convicting someone under these circumstances would create a dangerous precedent which would encourage people to flee rather than stand up for their rights due to fear of prosecution even if acting in defense against violence or threats thereof.