The legality of the Southern Ocean Sanctuary has been a matter of debate. This paper seeks to explain the Sanctuary as being both legal and illustrative of the development of international environmental law within a new, evolutionary framework. A teleological approach to statutory interpretation could construe the Convention in ways that are supportive of the non-lethal utilisation of cetaceans. Such an interpretation may be supported under the Vienna Convention, whereby if examples of previous practice demonstrating different interpretations of the language in question can be shown, then this practice is evidence that a different interpretation of the convention in question is legitimate. This has been the case with the International Whaling Commission. The paper concludes that the Southern Ocean Sanctuary may be regarded as being both a legal and authoritative example of the way in which the majority of the international community has viewed one area of global environmental concern.