United States v. Rockwell 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 was obtained through an illegal search and seizure. The case involved a defendant, Rockwell, who was charged with possession of a firearm in violation of the National Firearms Act. The government had obtained evidence of the firearm through an illegal search and seizure, and Rockwell argued that the evidence should be excluded from his trial. The Supreme Court held that the evidence obtained through the illegal search and seizure was admissible in the trial. The Court reasoned that the exclusionary rule, which prohibits the use of illegally obtained evidence in a criminal trial, did not apply in this case because the government had acted in good faith in obtaining the evidence. The Court also noted that the exclusionary rule was intended to deter police misconduct, and that the government had not acted in bad faith in this case. The Court's decision in United States v. Rockwell established that the exclusionary rule does not apply when the government has acted in good faith in obtaining evidence. This decision has been cited in numerous subsequent cases, and it has been used to support the argument that the exclusionary rule should not be applied when the government has acted in good faith.

Justice Field delivered the dissenting opinion in United States v. Rockwell, arguing that the majority's decision was contrary to both precedent and common sense. He argued that a contract between two parties should be interpreted according to its plain language, not by what one party may have intended or expected when they entered into it. In this case, he believed that the government had agreed to pay for all of Rockwell's services as an engineer on a project regardless of whether those services were completed or not; thus, he felt there was no basis for denying payment due under the terms of their agreement. Furthermore, Justice Field noted that if such contracts could be voided simply because one party did not fulfill their obligations then it would lead to great uncertainty in contractual relationships and ultimately harm commerce as well as public confidence in business dealings.