In the 1946 case of Sunal v. Large, Superintendent, Federal Prison Camp, the U.S. Supreme Court ruled that habeas corpus petitions could not be used as a substitute for an appeal process in criminal cases. The petitioners were eight conscientious objectors who had been convicted during World War II for refusing to report for civilian work as required by the Selective Training and Service Act of 1940. They argued that their convictions were invalid because they had been denied due process rights under the Fifth Amendment and equal protection rights under the Fourteenth Amendment. The Supreme Court disagreed with their argument stating that these issues should have been raised on direct appeal rather than through habeas corpus proceedings after conviction. The court emphasized that allowing such use of habeas corpus would undermine orderly appellate procedure and flood federal courts with frivolous claims from prisoners seeking release.

In the dissenting opinion for Sunal v. Large, Justice Frankfurter argued that habeas corpus should not be used as a substitute for an appeal process in cases where defendants have been convicted under statutes later found to be unconstitutional. He maintained that the majority's decision would open up floodgates of litigation from prisoners seeking release based on subsequent changes in law or legal interpretation, thus overburdening courts and undermining finality in criminal proceedings. Furthermore, he contended that such use of habeas corpus undermines its historical purpose - to provide relief from unlawful detention when no other remedy is available - by turning it into a tool for post-conviction review of legal errors made at trial. This could potentially lead to misuse and devaluation of this important constitutional safeguard against arbitrary imprisonment.