United States v. Villalonga was a United States Supreme Court case that dealt with the issue of whether a defendant could be convicted of a crime if the evidence presented at trial was obtained through an illegal search and seizure. The defendant, Villalonga, was charged with the illegal possession of firearms and ammunition. At trial, the prosecution presented evidence that was obtained through a search of Villalonga's home without a warrant. Villalonga argued that the evidence should be excluded because it was obtained in violation of the Fourth Amendment. The Supreme Court held that the evidence was admissible because the search was conducted in good faith and with probable cause. The Court reasoned that the officers had reasonable grounds to believe that the defendant was in possession of firearms and ammunition, and that the search was conducted in a reasonable manner. The Court also noted that the exclusionary rule, which prohibits the use of illegally obtained evidence, does not apply when the search is conducted in good faith and with probable cause. In conclusion, the Supreme Court held that the evidence obtained through the search of Villalonga's home was admissible at trial. The Court reasoned that the search was conducted in good faith and with probable cause, and that the exclusionary rule did not apply in this case.

In United States v. Villalonga, the Supreme Court was asked to decide whether a defendant who had been convicted of violating a federal law should be allowed to appeal his conviction on the grounds that he did not receive proper notice prior to trial. The majority opinion held that because the defendant had received sufficient notice before trial and failed to raise any objections at that time, he could not now challenge his conviction on procedural grounds. Justice Field dissented from this decision, arguing that due process requires adequate notice for all criminal defendants regardless of when they choose to object or appeal their convictions. He argued further that it would be unjust for courts to deny appeals based solely upon technicalities such as lack of timely objection when there is no evidence suggesting bad faith by either party in failing to comply with procedural requirements.