From the Overview: "As of November 2020, the Department of the Interior (DOI) employed nearly 3,400 law enforcement officers (LEOs) assigned to seven distinct organizational units within five DOI bureaus. These seven units are the Bureau of Land Management (BLM); Bureau of Indian Affairs (BIA); Bureau of Reclamation (BOR); U.S. Fish and Wildlife Service's (FWS's) Office of Law Enforcement (OLE) and Division of Refuge Law Enforcement (REF); National Park Service (NPS); and U.S. Park Police (USPP) within NPS. DOI's law enforcement contingent is the fourth-largest among executive branch departments, after the Departments of Homeland Security, Justice, and Veterans Affairs. Law enforcement on lands owned and administered by the federal government is of perennial interest to Congress. This includes issues related to funding, jurisdictional disputes between federal and nonfederal law enforcement agencies, and more recent concerns around excessive force and police-community relations."
CRS In Focus, IF11709
Congressional Research Service: https://crsreports.congress.gov/