In Lutwak et al. v. United States, the defendants were convicted of conspiracy to commit offenses against the U.S., specifically for arranging fraudulent marriages between American citizens and Polish nationals in order to secure immigration visas for the latter group. The Supreme Court upheld these convictions, rejecting arguments that evidence from co-conspirators should not have been admitted at trial and that there was insufficient proof of a criminal agreement among all parties involved. The court ruled that while statements made by conspirators after their scheme had ended could not be used as evidence against other members of the conspiracy, testimony about actions taken during its course was admissible. Furthermore, it held that although some participants may have believed they were engaging in legitimate marriages rather than a criminal plot, this did not negate the existence or illegality of said plot if others knowingly participated with fraudulent intent. This case established important precedents regarding how courts interpret conspiracies under federal law: namely, focusing on collective action over individual knowledge or intent; allowing certain types of hearsay evidence; and recognizing marriage fraud as a serious crime.

In the dissenting opinion for Lutwak et al. v. United States, Justice Jackson disagreed with the majority's view that fraudulent marriages could be used as evidence of conspiracy to commit immigration fraud. He argued that marriage, even if entered into for ulterior motives, is a legal act and cannot be considered illegal simply because it was done for personal gain or convenience. Furthermore, he contended that using such marriages as evidence would set a dangerous precedent where any lawful act could potentially be deemed criminal based on subjective interpretations of intent or motive behind it. Additionally, he expressed concern over potential invasion of privacy rights in probing into marital relationships and intentions behind them.