Pacta sunt servanda & Jus cogens

Pacta sunt servanda 

(Latin for "agreements must be kept", in Portuguese - "os pactos devem ser respeitados" ou "os acordos devem ser cumpridos"), is a brocard, a basic principle of civil law and of international law.

In its most common sense, the principle refers to private contracts, stressing that contained clauses are law between the parties, and implies that nonfulfillment of respective obligations is a breach of the pact.

In civil law jurisdictions this principle is related to the general principle of correct behavior in commercial practice — including the assumption of good faith — is a requirement for the efficacy of the whole system, so the eventual disorder is sometimes punished by the law of some systems even without any direct penalty incurred by any of the parties. 

However, common law jurisdictions usually do not have the principle of good faith in commercial contracts, therefore it is inappropriate to state that pacta sunt servanda includes the principle of good faith.

With reference to international agreements, "every treaty in force is binding upon the parties to it and must be performed by them in good faith." Pacta sunt servanda is related to good faith, while pacta sunt servanda does not equate with good faith. This entitles states to require that obligations be respected and to rely upon the obligations being respected. This good faith basis of treaties implies that a party to the treaty cannot invoke provisions of its municipal (domestic) law as justification for a failure to perform. 

However, with regards to the Vienna Convention and the UNIDROIT Principles (International Institute for the Unification of Private Law) it should be kept in mind that these are heavily influenced by civil law jurisdictions. To derive from these sources that pacta sunt servanda includes the principle of good faith is therefore incorrect.

The only limit to pacta sunt servanda are the peremptory norms of general international law, called jus cogens (compelling law). The legal principle clausula rebus sic stantibus, part of customary international law, also allows for treaty obligations to be unfulfilled due to a compelling change in circumstances.

Jus Cogens

Jus  cogens (compelling law), is the modern concept of international law that posits norms so fundamental to the public order of the international community that they are potent enough to invalidate established by states.

The most notable appearance of jus cogens is in article 53 of the Vienna Convention on the Law of Treaties, where the term is rendered in English as “peremptory norm”:

     "  A treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm

     of general international law. 

     

       For the purposes of the present Convention, a peremptory norm of general 

     international law is a norm accepted and recognized by the international community

     of States as a whole as a norm from which no derogation is permitted and which can 

     be modified only by a subsequent norm of general international law having the same

     character. "

The Vienna Convention further provides that:

    "  If a new peremptory norm of general international law emerges, any existing treaty

     which is in conflict with that norm becomes void and terminates."

Probably no rule better fits the definition of jus cogens than pacta sunt servanda, for it is essential to the theory of both conventional and customary international law that contracts between states be legally binding.

The pacta sunt servanda rule is neither a rule of conventional nor customary international law, but rather a norm fundamental to the legal system from which both treaty and customary rules derive.

The distinctive character essence of jus cogens is such, as to blend the concept into traditional notions of natural law. Such a blending makes sense both historically and functionally.

Historically, it is significant that the proponents of the idea of peremptory norms invalidating treaty rules were, in no small measure, reacting to the abuses of Nazism during the Second World War. They rejected the positivist proposition that state acts, even the making of treaties, should be always thought capable of making binding law.

Functionally, a rule of jus cogens is, by its nature and utility, a rule so fundamental to the international community of states as a whole that the rule constitutes a basis for the community’s legal system.

Perforce and per article 53, a rule of jus cogens is ordinarily non-derogable and invalidates subsequent norms generated by treaty or by custom, that is, by the ordinary consensual forms of international legislation. Thus it is a sort of international law that, once ensconced, cannot be displayed by states, either in the their treaties or in their practice.

Jus cogens therefore functions like a natural law that is so fundamental that states, at least for the time being, cannot avoid its force.

fonte (1) “Philosophy of Law: Classic and Contemporary Reading” edited by Larry May and Jeff Brown

fonte (2) wikipedia