In the United States v. Lewis case of 1950, the Supreme Court ruled on a matter involving federal jurisdiction over crimes committed in Indian Country. The defendant, an enrolled member of the Yakima Tribe named George Lewis Jr., was charged with assault within Indian Country under federal law. However, he argued that since his crime occurred on land allotted to him and held in trust by the U.S government as part of a reservation, it should be considered outside "Indian country" and thus not subject to federal jurisdiction. The court disagreed with this interpretation. It found that lands held in trust for individual Indians or tribes are still considered part of "Indian country," regardless if they're located within reservations or not. Therefore, such areas fall under federal criminal jurisdiction when offenses involve Native Americans. This ruling affirmed that Congress has broad power to define what constitutes "Indian country" for purposes of criminal law enforcement and can include lands individually owned by tribal members but held in trust by the U.S government.

The dissenting opinion in the United States v. Lewis case argued that the majority's decision to uphold Lewis' conviction for refusing induction into military service was incorrect. The dissenters believed that the Selective Service System had not provided sufficient evidence to prove beyond a reasonable doubt that Lewis knowingly and willfully refused induction, which is required under criminal law standards. They also criticized the majority's interpretation of "knowingly" as merely requiring awareness of one's actions rather than an understanding of their illegality, arguing this could lead to unjust convictions for individuals who were unaware they were breaking any laws. Furthermore, they contended that there was no clear proof presented at trial showing whether or not Lewis understood his obligation under selective service laws when he refused induction.