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Application of Treties and Customary International Law in UK

The purpose of this paper is to analyze UK’s position to the application of the rules of international law, both conventional and customary, in its domestic legal system. To this end, the decisions of the courts of UK are examined. As to the rules of treaties, they are not self-executing in UK. Rights and obligations arising from treaties can be implemented in national courts only when they are transformed into national law by an Act of Parliament. This does not mean, however, that a treaty cannot be looked at or construed. The provisions of treaties may be referred to when an Act of Parliament expressly or implicitly gives effect to them. In such cases, the courts apply the rules of international law on treaty interpretation. Where the terms of an Act are unambiguous, they prevail over a treaty in question. Yet, subject to a preliminary test of ambiguity, the courts construe national laws in conformity with treaties. As to the rules of customary international law, it seems to be established that they are automatically part of the law of the land, without the intervention by Parliament. However, the crimes of customary international law cannot be assimilated into domestic law without legislation by Parliament. Therefore, English law sees two different approaches to the application of customary international law in domestic law. The determinant factor of the application of international law in domestic law is the constitutional principle, that is, the principle of Parliamentary sovereignty. This principle works as an filter through which the methods of the application of international law in national courts are determined. The doctrines of incorporation and transformation serve as a useful means to analyze the attitudes of courts.