In the 1950s through the 1970s, most federal civilian police (Career Series 0083) employed by the various federal agencies (DOD, Veterans Admin, GSA/Federal Protective Service, Library of Congress, etc.) were defined in the statutes as "Special Police" (some DOD police units on Army and Navy bases were referred to as "Security Police"). As an example, Title 40 United States Code, which established the powers of the Federal Protective Service, stated that the Commissioner of the General Services Administration has "the authority to designate certain employees as Special Police for the purpose of protecting life and property at facilities under the control of GSA". By the 1980's, when I started my career as a Veterans Administration Police Officer and then a DOD cop on an Army base, the terms Special and Security had been removed from the books and 0083's were referred to simply as Police Officers, with badges and patches being changed to the new title. (As a reference, in the federal govt Career Series - similar to military MOS - for law enforcement positions, Series 0085 is Security Guard; 0083 is Police Officer; 1811 is Criminal Investigator/Special Agent. Federal park rangers, corrections officers, and conservation/wildlife officers have their own career codes, which I don't recall at the moment). Currently, within the fed govt, the term "Special Police" is only used for private security contractors hired by an agency who are commissioned with limited police powers when on duty at their assigned facility (an example would be the security staff at the National Archives - who protect the Declaration of Independence among other items - who are called the National Archives & Records Service Special Police).