In the 1902 case of Pickens v. Roy, the United States Supreme Court addressed a dispute over land ownership in Louisiana. The plaintiff, Pickens, claimed that he had purchased and owned certain lands under a patent from the United States government. However, Roy argued that these lands were part of his property based on an older Spanish grant which was confirmed by an act of Congress before Pickens' purchase took place. The court ruled in favor of Roy stating that when there is conflict between two titles to land - one derived directly from the federal government and another recognized by it through legislation confirming previous foreign grants - priority should be given to the latter if it predates the former's issuance date. Therefore, even though both parties held legitimate claims according to their respective sources (U.S patent for Pickens and Congressional confirmation for Roy), precedence was given to earlier claim i.e., Roy’s Spanish grant.

In the dissenting opinion for Pickens v. Roy, Justice Harlan disagreed with the majority's interpretation of the law and its application to this case. He argued that Congress had clear authority over Indian affairs and could regulate them as it saw fit, including modifying or abrogating treaties made with Native American tribes. However, he believed that in this particular instance, Congress did not intend to interfere with existing property rights granted under previous treaties when it passed legislation opening up certain lands for settlement by non-Indians. Therefore, he would have upheld the lower court's decision granting an injunction against interference with these property rights on behalf of members of Choctaw tribe who claimed ownership based on a treaty provision.