Public Law 83-280 (commonly referred to as "Public Law 280" or "PL-280"), was originally enacted in 1953 and did two things to alter the usual allocation of criminal jurisdiction in Indian Country. First, on the reservations to which it applied, it took away the federal government’s authority to prosecute Indian Country crimes based on 18 USC 1152 (the Indian Country General Crimes Act) and 18 USC 1153 (the Major Crimes Act). Second, it authorized the states of Alaska, California, Minnesota, Nebraska, Oregon, and Wisconsin to prosecute most crimes that occurred in Indian Country. Exceptions were set forth for a few topic areas and on a few reservations, but the main result of Public Law 280 is that for most reservations in the six named states, federal criminal jurisdiction became extremely limited while state jurisdiction was greatly expanded.
Public Law 280 altered the allocation of federal and state criminal jurisdiction. Public Law 280 did not reduce nor expand tribal criminal jurisdiction.
The law did not provide for the consent of affected tribes. Thus, criminal laws in those States became effective over Indians within as well as outside Indian country. PL 280 provided no financial support for the newly established state law enforcement responsibilities. It also did not expressly abolish tribal justice system jurisdiction, diminish the federal government’s overall trust responsibility to tribes, or reject federal obligations to provide services to tribes other than federal law enforcement.
Court decisions have attempted to define the jurisdictional contours of PL 280; however, they have also raised some areas of uncertainty: regulatory versus prohibitory laws. The U.S. Supreme Court has declared that "regulatory" rather than "prohibitory" state criminal laws are outside the scope of jurisdiction conferred by PL 280. This distinction has generated considerable litigation.
Source: US DOJ, Office of Justice Programs, National Institute of Justice, "Public Law 280 and Law Enforcement in Indian Country – Research Priorities." Dec. 2005. https://www.ojp.gov/pdffiles1/nij/209839.pdf