PULP MILLS (JUDGMENT) 83 aquatic environment with respect to activities which may be liable to cause transboundary harm, carry out an environmental impact assessment. As the Court has observed in the case concerning the Dispute Regarding Navigational and Related Rights, “there are situations in which the parties’ intent upon conclusion of the treaty was, or may be presumed to have been, to give the terms used — or some of them — a meaning or content capable of evolving, not one fixed once and for all, so as to make allowance for, among other things, developments in international law” (Dispute Regarding Navigational and Related Rights (Costa Rica v. Nicaragua), Judgment, I.C.J. Reports 2009, p. 242, para. 64). In this sense, the obligation to protect and preserve, under Article 41 (a) of the Statute, has to be interpreted in accordance with a practice, which in recent years has gained so much acceptance among States that it may now be considered a requirement under general international law to undertake an environmental impact assessment where there is a risk that the proposed industrial activity may have a significant adverse impact in a transboundary context, in particular, on a shared resource. Moreover, due diligence, and the duty of vigilance and prevention which it implies, would not be considered to have been exercised, if a party planning works liable to affect the régime of the river or the quality of its waters did not undertake an environmental impact assessment on the potential effects of such works. 205. The Court observes that neither the 1975 Statute nor general international law specify the scope and content of an environmental impact assessment. It points out moreover that Argentina and Uruguay are not parties to the Espoo Convention. Finally, the Court notes that the other instrument to which Argentina refers in support of its arguments, namely, the UNEP Goals and Principles, is not binding on the Parties, but, as guidelines issued by an international technical body, has to be taken into account by each Party in accordance with Article 41 (a) in adopting measures within its domestic regulatory framework. Moreover, this instrument provides only that the “environmental effects in an EIA should be assessed with a degree of detail commensurate with their likely environmental significance” (Principle 5) without giving any indication of minimum core components of the assessment. Consequently, it is the view of the Court that it is for each State to determine in its domestic legislation or in the authorization process for the project, the specific content of the environmental impact assessment required in each case, having regard to the nature and magnitude of the proposed development and its likely adverse impact on the environment as well as to the need to exercise due diligence in conducting such an assessment. The Court also considers that an environmental impact assessment must be conducted prior to the implementation of a project. Moreover, once 73