The present study considers the legislative history of article 218 of the 1982 UN Convention on the Law of the Sea. This article deals with the enforcement by port States of vessel-source pollution perpetrated outside the internal waters, the territorial sea or the exclusive economic zone of such States in violation of applicable international rules and standards established through the competent international organisation or general diplomatic conference. It lays down the basic legal regime of a port State's competence in respect of pollution control when a vessel is voluntarily within its port or at its offshore terminal.