In the 1891 case of Dunwoody v. United States, the Supreme Court ruled on a dispute involving land patents issued by the U.S. government. The plaintiff, Dunwoody, claimed that he had purchased lands from individuals who had received them as part of military bounty land warrants under an act passed in 1855. However, these lands were also included in a subsequent patent granted to railroad companies under an act passed in 1864 for construction purposes. The main issue was whether or not the issuance of patents to railroads superseded previous grants made through military bounty land warrants and if those original grantees could legally transfer their rights to others (like Dunwoody). The court held that once a patent is issued by the government it becomes "irrevocable" and can't be annulled or set aside unless there's evidence of fraud or mistake; therefore, earlier claimants like Dunwoody have no legal standing against later recipients such as railroads when both parties hold valid patents from different times for same piece(s) of property. This decision reinforced principles regarding federal power over public lands and clarified how conflicting claims based on separate acts should be resolved - favoring most recent grantee with valid patent.

In the dissenting opinion for Dunwoody v. United States, 1891, it was argued that the court erred in its interpretation of the law regarding postal fraud. The dissenting justices believed that there had been a misinterpretation of what constituted as "schemes to defraud" under the relevant statute. They contended that not all deceitful or dishonest acts should be considered fraudulent if they do not result in financial or property loss for another party. In this case, while Dunwoody may have acted dishonestly by using false names and addresses to send mail, he did not cause any monetary harm or loss to others; hence his actions shouldn't be deemed fraudulent under this specific law according to these justices' view point. Furthermore, they expressed concern about broad interpretations of laws which could potentially criminalize harmless deceptions and infringe upon individual liberties without just cause.