In the O'Sullivan v. Felix case of 1913, the U.S Supreme Court ruled that a patent owner cannot extend their monopoly by obtaining a new patent for an invention that is merely an obvious variation of the original patented product. The plaintiff, O'Sullivan, held patents for rubber heels and claimed that Felix had infringed upon his rights by manufacturing similar products. However, it was found that Felix's designs were not identical to those patented by O'Sullivan but rather slight modifications or improvements on them. The court concluded these changes were so trivial they did not constitute infringement as they would have been obvious to anyone skilled in this particular field (rubber heel production). Therefore, no violation of patent rights occurred according to Justice Lurton who delivered the opinion of the court.

The dissenting opinion in the case of O'Sullivan v. Felix argued that the majority's decision was inconsistent with previous rulings and interpretations of habeas corpus law. The dissent, led by Justice Holmes, disagreed with the majority's view that a federal court could not release a prisoner on habeas corpus if he had been indicted but not yet tried for an offense under state law. They contended that this interpretation effectively denied prisoners their right to challenge unlawful detention before trial. Furthermore, they believed it contradicted earlier decisions which held that federal courts could intervene in such cases when there was evidence of constitutional violations or other legal errors at play during pretrial proceedings. Therefore, according to them, the ruling undermined both individual rights and federal authority over state criminal justice systems.