1. ECJ, Case 26/62 van Gend & Loos v. Nederlandse Administratie der Belastingen [1963] ECR 1; ECJ, Case 6/64 Costa v. E.N.E.L. [1964] ECR 1251.
2. ECJ, Opinion 1/91 European Economic Area 1 [1991] ECR I-6102 (para. 21); ECJ, Case 294/83 Les Verts v. European Parliament [1986] ECR 1339, para. 23; ECJ, Case 2/88 Zwartveld [1990] ECR I-3365; CFI, Case T-115/94 Opel Austria v. Council [1997] ECR II-39 (para. 62).
3. See the discussions during the 1970s and 1980s: P.J.G. Kapteyn, ‘The Domestic Law Effect of Rules of International Law within the European Community System of Law and the Question of Self-Executing Character of GATT-Rules’, International Lawyer (1974), p. 74; R. Kovar, ‘Les accords liant les Communautés Européennes et l’ordre juridique communautaire’, R.M.C. (1974), p. 345; H. Schermers, ‘Community Law and International Law’, CML Rev (1975), pp. 77–90; H. Krück, Völkerrechtliche Verträge im Recht der Europäischen Gemeinschaften (Berlin, 1977); O. Jacot-Guillarmod, Droit Communautaire et Droit International Public (Geneva, 1979); P. Pescatore, ‘External relations in the Case-law of the Court of Justice of the European Communities’, CML Rev (1979), pp. 615–645; G. Bebr, ‘Agreements Concluded by the Community and their Possible Direct Effect: From International Fruit to Kupferberg’, CMLRev. (1983), pp. 35–73; P. Pescatore, ‘Die Rechtsprechung des Europäischen Gerichtshofs zur gemeinschaftlichen Wirkung völkerrechtlicher Abkommen’; in Festschrift für H.Mosler, Völkerrecht als Rechtsordnung, internationale Gerichtsbarkeit Menschenrechte (Berlin, 1983), p. 661; J. Schwarze, ‘Das allgemeine Völkerrecht in den innergemeinschaftlichen Rechtsbeziehungen’, EuR (1983), p. 1; C. Tomuschat, ‘Zur Rechtswirkung der von der Gemeinschaft abgeschlossenen Verträge in der Gemeinschaftsrechtsordnung’, in G. Lücke and G. Rees and M. Will (eds.), Rechtsvergleichung Europarecht und Staatenintegration, Gedächtnisschrift für L.J. Constantinesco (Cologne, 1983), p. 809; P. VerLoren van Themaat, ‘The impact of the Case-law of the Court of Justice of the European Communities on the Economic World Order’, 82 Michigan Law Review (1984), pp. 1422–1438; J.H.J. Bourgeois, ‘Effects of International Agreements in European Community Law: Are the dice cast?’, 82 Michigan Law Review (1984), pp. 1250–1273; A. Giardina, ‘International Agreements of the Member States and Their Construction by the Court of Justice’, in Capotorti, C.D. Ehlermann, J. Frowein, F.Jacobs, Joliet, Koopmans/R. Kovar (eds.), Festschrift for P.Pescatore: Du droit international au droit de l’intégration, (Nomos Verlagsgesellschaft, Baden-Baden, 1987), p. 246.
4. The landmark cases were the following: ECJ, Case 26/62 van Gend & Loos v. Nederlandse Administratie der Belastingen [1963] ECR 1; ECJ, Case 6/64 Costa v. E.N.E.L. [1964] ECR 1251; ECJ, Case 106/77 Simmenthal v. Ammistrazione delle finanze dello Stato [1978] ECR 644.
5. ECJ, Case 22/70 Commission v. Council (AERT or ERTA), [1971] ECR 263; ECJ, Case 181/73 Haegeman v. Belgium [1974] ECR 449 (at 460, para. 2/6); ECJ, Case 21-24/72 International Fruit Company NV et al. v. Produktschap voor Groenten en Fruit [1972] ECR 1219.