The norm pacta sunt servanda, which has constituted “since times immemorial the axiom, postulate and categorical imperative of the science of international law” and has very rarely been denied on principle, is undoubtedly a positive norm of general international law. But the meaning of this norm is controversial. Most writers lay the accent on the term servanda. One school of thought affirms that “treaties” are always binding, whereas a second tells us that the norm can only mean that valid treaties are binding.; Within this second school of thought some writers object that the norm appears as a deus ex machina, as international law does not lay down rules for the validity of international treaties, whereas others maintain, that not all, but only certain treaties are binding, that the norm admits “exceptions,” or speak of the relativité de la règle pacta sunt servanda.