[850] Since the time of Grotius the science of the Law of Nations has not ceased attempting a satisfactory classification of the different kinds of treaties. See Heffter, §§ 88-91; Bluntschli, §§ 442-445; Martens, I. § 113; Ullmann, § 82; Wheaton, § 268 (following Vattel, II. § 169); Rivier, II. pp. 106-118; Westlake, I. p. 283, and many others.
Binding Force of Treaties.
§ 493. The question as to the reason of the binding force of international treaties always was, and still is, very much disputed. That all those publicists who deny the legal character of the Law of Nations deny likewise a legally binding force in international treaties is obvious. But even among those who acknowledge the legal character of International Law, unanimity by no means exists concerning this binding force of treaties. The question is all the more important as everybody knows that treaties are sometimes broken, rightly according to the opinion of the one party, and wrongly according to the opinion of the other. Many publicists find the binding force of treaties in the Law of Nature, others in religious and moral principles, others[851] again in the self-restraint exercised by States in becoming a party to a treaty. Some writers[852] assert that it is the contracting parties' own will which gives binding force to their treaties, and others[853] teach that such binding force is to be found im Rechtsbewusstsein der Menschheit—that is, in the idea of right innate in man. I believe that the question can satisfactorily be dealt with only by dividing it into several different questions and by answering those questions seriatim.
[851] So Hall, § 107; Jellinek, "Staatenverträge," p. 31; Nippold, § 11.
[852] So Triepel, "Völkerrecht und Landesrecht" (1899), p. 82.
[853] So Bluntschli, § 410.
First, the question is to be answered why treaties are legally binding. The answer must categorically be that this is so because there exists a customary rule of International Law that treaties are binding.
Then the question might be put as to the cause of the existence of such customary rule. The answer must be that such rule is the product of several joint causes. Religious and moral reasons require such a rule quite as much as the interest of the States, for no law could exist between nations if such rule did not exist. All causes which have been and are still working to create and maintain an International Law are at the background of this question.
And, thirdly, the question might be put how it is possible to speak of a legally binding force in treaties without a judicial authority to enforce their stipulations. The answer must be that the binding force of treaties, although it is a legal force, is not the same as the binding force of contracts according to Municipal Law, since International Law is a weaker law, and for this reason less enforceable, than Municipal Law. But just as International Law does not lack legal character in consequence of the fact that there is no central authority[854] above the States which could enforce it, so international treaties are not deficient of a legally binding force because there is no judicial authority for the enforcement of their stipulations.