The Act mandated a transfer of federal law enforcement authority within certain tribal nations to state governments in six states: California, Minnesota (except the Red Lake Nation), Nebraska, Oregon (except the Warm Springs Reservation), Wisconsin (except later the Menominee Reservation) and, upon its statehood, Alaska. Other states were allowed to elect similar transfers of power, at the initiative of state residents. Since then, Nevada, South Dakota, Washington, Florida, Idaho, Montana, North Dakota, Arizona, Iowa, and Utah have assumed some jurisdiction over crimes committed by tribal members on tribal lands.
The Act added to a complex matrix of jurisdictional conflict that defined tribal governance at the end of the 20th century. In various states, local police, tribal police, BIA police, the FBI are the arms of a law enforcement system that enforces laws of tribes, states and the federal government.
Under the Act, states, local sheriffs and state law enforcement agencies take tribal members to state courts for prosecution in cases arising from criminal matters within reservation boundaries. But most tribal governments and pueblos have also adopted their own codes, and administer court systems to adjudicate violations of the code.
In states where the Act has not been applied, Bureau of Indian Affairs (BIA) police respond to major crimes on reservations or pueblos. The FBI joins in investigations of the most serious criminal matters such as murders or kidnappings. In those states, when allegations against tribal members arise from crimes on a reservation, the United States Attorney cites violations of the United States Code in a United States district court. Tribal and pueblo police also enforce local codes in "non-PL 280" states.