The United States v. Giles and Others was a Supreme Court case in which the court ruled that the federal government had authority to prosecute individuals for crimes committed against Native Americans on tribal lands, even if those individuals were not members of the tribe or citizens of the United States. The defendants in this case were accused of murdering two Creek Indians while they were living on their own tribal land, and argued that since they weren't part of any tribe or U.S citizen, they couldn't be prosecuted by federal authorities. However, Chief Justice John Marshall wrote an opinion stating that Congress has power over all Indian affairs within its borders and can punish anyone who commits a crime against them regardless of citizenship status or membership in a particular tribe. This ruling established precedent for future cases involving similar issues regarding Native American rights under U.S law and reaffirmed Congress's ability to protect indigenous people from violence perpetrated by non-Indians on their ancestral lands

The dissenting opinion in the United States v. Giles and Others case argued that Congress had no authority to pass a law punishing individuals for crimes committed before the passage of said law. The dissenters believed that such an act would be unconstitutional as it violated the Ex Post Facto Clause, which prohibits laws from being passed retroactively to punish individuals for actions taken prior to its enactment. Furthermore, they argued that if Congress was allowed to pass such a law then it could potentially lead to arbitrary punishments and infringe on citizens' rights by allowing them to be punished without due process or fair warning of potential consequences. They concluded by stating that any attempt at passing a retrospective criminal statute should not be tolerated as it is contrary to fundamental principles of justice and liberty enshrined in our Constitution.