Affiliated instruments and organizations P rotocol Relating to Intervention on the High Seas in Cases o f M arine Pollu tion by Sub­ stances Other than Oil, London, 2 Novem­ ber 1973. Entered into force on 30 March 1983. 42 Parties (44.91 per cent of world tonnage) by 1 June 1999. One Signatory without ratification or approval. The basic objective o f the Protocol is to extend the 1969 Convention to apply also to sub­ stances other than oil, such as noxious sub­ stances, liquefied gases, and radioactive substances.