The music for the Olympic anthem was composed by Spiros Samaras, to words by Kostas Palamas, for the first Games in Athens in 1896. Various musical arrangements went on to be played at the opening ceremonies. In 1958, in Tokyo, the IOC Session decided that the Samaras/Palamas composition would be the official Anthem as of the 1960 Games (Squaw Valley and Rome).
The Olympic anthem is one of the Olympic properties:
Olympic Charter: Chapter 1, Rule 7.4 and its Bye-law and Rule 12