Issue, underlying concepts and approaches. Under general international law, all States must
undertake an environmental impact assessment of their planned activities that may have a significant impact in a transboundary context. In 1992, as part of the Rio Declaration principles, all the States Members of the United Nations undertook to provide a “prior and timely notification and relevant information to potentially affected States” and to “consult with those States at an early stage and in good faith” on such planned activities.