ABSTRACT
Jus cogens The concept that a treaty concluded in violation of a norm of jus cogens is null and void is highly controversial. Any analysis of the concept requires an investigation into the relevance in international law of private law analogies and into the extent to which, if at all, there exists an objective notion of international public policy consisting of legal rules from which states are not permitted to derogate by way of international agreement. But first, you may ask, what is jus cogens? Suy defines it as ‘the body of those
not, under pain of absolute nullity, depart from them in virtue of particular agreements’.30 From this definition it will be noted that the concept of jus cogens is wholly general in nature and applicable to any system of law. It is not a concept which has been specially developed within the framework of public international law; on the contrary, it derives from, and is deeply embedded in, particular systems of private law. The origin of the notion of jus cogens has been traced back to Roman law. The maxim jus publicum privatorum pactis mutari non potest is to be found in the Digest. The jus publicum was to be understood in a wide sense as embracing not only public law in the strict sense (that is to say, the law governing relations between individuals and the state) but also rules from which individuals were not permitted to depart by virtue of particular agreements. The pervading influence of this general notion can be recognised by the development of such concepts as ordre public and öffentliche Ordnung in French and German law respectively, and by the gradual establishment in common law of the principle that certain types of contract are, by their very nature, injurious to society and therefore contrary to public policy. The genesis of this principle in English law can be traced back to Elizabethan times, although it was only in the 18th century that its foundations were effectively laid in a series of decisions proclaiming, in somewhat vague and indeterminate language, the nullity of contracts injurious to the public good or contra bonos mores.31
