129 Furthermore, the fact that, in the context of applying European Union environmental legislation, certain matters contributing to the pollution of the air, sea or land territory of the Member States originate in an event which occurs partly outside that territory is not such as to
call into question, in the light of the principles of
customary international law capable of being relied upon in the main proceedings, the full applicability of European Union
law in that territory (see to this effect, with regard to the application of competition
law, Ahlström Osakeyhtiö and Others v Commission, paragraphs 15 to 18, and, with regard to hydrocarbons accidentally spilled beyond a Member State's territorial sea, Case C ‑ 188 / 07 Commune de Mesquer [2008] ECR I ‑ 4501, paragraphs 60 to 62).
Doing so effectively
calls for research skills beyond those that students acquire through working with domestic legal resources.56 Mary Rumsey explains that students must go beyond their dependence on domestic databases to learn how to access the different resources relevant to
international and comparative
law.57 She describes, as examples, the need to find
customary international law through treaties,
laws of other nations, diplomatic correspondence, and scholarly works, and she points out that civil
law research requires much more emphasis on statutes and scholarship than on the case
law that plays such a dominant role in American legal analysis.58 While there have been significant advances in access to foreign and
international legal sources, there are still substantial barriers, 59 and the research methods needed to obtain these resources can be different (in ways either subtle or stark) from those that apply to domestic
law.