5150 is the section of the California Welfare and Institutions Code dealing with involuntary confinement of a mentally disordered person. (I.e. California law consists of 29 codes, of which the Welfare and Institutions Code is one, and 5150 is a section number in that code.) Also the name of an old Van Halen album. It is also a track on Da Luniz' album "Operation Stackola".