In Iannelli et al. v. United States (1974), the U.S Supreme Court ruled that defendants could be prosecuted for both conspiracy and the substantive offense which was the object of that conspiracy, without violating the Double Jeopardy Clause of the Fifth Amendment to the Constitution. The case involved a group who were charged with conspiring to conduct an illegal gambling business and conducting such a business in violation of federal law. They argued that these charges constituted double jeopardy as they were being punished twice for essentially one crime - running an illegal gambling operation. However, by 8-1 majority decision, Justice Potter Stewart writing for court held that Congress intended separate punishments under each statute because each provision required proof of a fact which other did not; thus it does not violate Double Jeopardy Clause.

In the dissenting opinion for Iannelli et al. v. United States, Justice Douglas argued that the defendants' convictions for both conspiracy and substantive offenses violated their protection against double jeopardy under the Fifth Amendment of the Constitution. He contended that a single agreement to commit an offense should not be treated as separate from committing the actual crime itself, as it essentially punishes individuals twice for one criminal act or transaction. The majority's decision to uphold such dual prosecutions was seen by Justice Douglas as a departure from established legal principles and precedent which traditionally safeguarded against cumulative punishments in this context.