Page "Known Space" Paragraph 57

The ARM is the police force of the United Nations.

ARM originated as an acronym for " Amalgamation of Regional Militia ", though this is not a term in current usage by the time of the Known Space novels.

An agent of the ARM, Gil Hamilton, is the protagonist of Niven's sci-fi detective stories, a series-within-a-series gathered in the collection Flatlander ( Confusingly, " Flatlander " is also the name of an unrelated Known Space story.