Merryman v. Bourne et al. was a United States Supreme Court case that dealt with the issue of habeas corpus. The case was brought by John Merryman, a Maryland resident who had been arrested by Union troops during the Civil War and held without trial. Merryman argued that his arrest was unconstitutional and that he should be released on habeas corpus. The Supreme Court agreed with Merryman, ruling that the suspension of habeas corpus was unconstitutional and that Merryman should be released. The ruling was significant because it established the principle that the federal government could not suspend habeas corpus without the approval of Congress. The decision also established the principle that the federal government could not interfere with the rights of citizens without due process of law. The ruling was a major victory for civil liberties and helped to ensure that the federal government could not arbitrarily detain citizens without cause.

In Merryman v. Bourne et al., the Supreme Court was asked to decide whether or not a military officer had the authority to suspend habeas corpus during wartime without congressional approval. The majority opinion held that Congress alone has this power, and thus any suspension of habeas corpus by a military officer is unconstitutional. Justice Field dissented from this decision, arguing that in times of emergency it is necessary for the President as Commander-in-Chief to have some degree of control over civil liberties in order to protect national security interests. He argued that while Congress should be consulted on such matters, ultimately it is up to the President's discretion when faced with an imminent threat against public safety and welfare.