A glimpse of Lassa Oppenheim ’s Definition of International Law

Author: Evangelia Linaki, Research Associate

During the course of time, there have been many distinguished personae, such as Hugo Grotius, Jeremy Bentham and Hersch Lauterpacht, who not only contributed to the development of legal methodology and theory of International Law but also put a great deal of effort to define International Law.Nevertheless, herein the attention will be dedicated to Lassa Oppenheim and an effort will be made for a concise overview of his thoughts on the nature of International Law to be provided.

Lassa Francis Laurence Oppenheim ((Beatson, Jack & Zimmermann Reinhard (eds.), Jurists Uprooted: German-speaking Émigré Lawyers in Twentieth-century Britain, at 583-585 (2004).))was born near Frankfurt, Germany in 1858 and died in Cambridge, the United Kingdom in 1919. Born to a wealthy Jewish father, he had the opportunity to receive extensive education, as in 1878 he started studying not only law with the then most prominent German lawyers but also metaphysics, forensic medicine and psychology.It is quite admirable that in 1889, despite the fact that he was a Jew and could have suffered the discrimination most of the Jewish underwent in the academic environment during that time, he was appointed extraordinarius professor in Freiburg, Germany with criminal law as his major subject. However, as he was aiming for a full professorship, he moved to Basle, Switzerland, where he accomplished his ambition in 1893.Due to unknown reasons, though, Oppenheim decided to move to London, the United Kingdom in 1895 where he started studying International Law. Quickly becoming an expertise in the field, he started teaching, whereas especially after his naturalisation in 1900 he kept providing the Foreign Office with legal advice. The turning point in his career was the publication of his treatise named “International Law” in 1905-1906, which led to his appointment as a Whewell Professor at Cambridge University from 1908 until 1919. His famous treatise, although it has undergone major changes, has succeeded in remaining relevant, since it has been republished by Oppenheim’s successors nine times so far.

His treatise International Law begins with the definition of the Law of Nations or International Law. It has to be pointed out that herein the second edition of the treatise is relied upon and not one of the latest, since Oppenheim was in charge of the editing for the first three editions ((See id., at 585.)). In view of the fact that this piece of work has undergone major changes in the next editions, there is a need to stay close to the ones on which the creator had still a say.

According to Oppenheim, “Law of Nations or International Law (Droit des gens, Völkerrecht) is the name for the body of customary and conventional rules which are considered legallybinding by civilised States in their intercourse with each other ((Oppenheim, Lassa, International Law: A Treatise, Vol. I, at 3 (1912).)).” It is interesting that right after the definition he goes on to distinguish among universal, general and particular International Law, in which case the first is binding upon all civilised States without exception, the second is binding upon a considerable number of States including the leading powers and the last one refers only to a small number of States ((See id.)). Moreover, he accepts the existing distinction between privateand public International Law, highlighting that only the latter represents the Law of Nations, which is to be observed by States only and not individuals ((See id., at 4.)).

As it was highly contested whether International Law is truly law and, thus, legally binding, Oppenheim tries through defining the notion of “law” to prove that International Law itself is to be abided by. Before providing the definition of law, he dismisses the argument that there has to be a sovereign political authority which sets and enforces rules for human conduct ((See id., at 5.)). According to his train of thought, he first points out that on the international plane it is impossible to have a central authority over and above sovereign States, a fact which does not,however, deprive International Law of its legally binding character ((See id.)). According to him, those who claim the opposite imply that a body of rules which refers only to written law and that customary law is applied by courts of a State in the same way as the written one ((See id.)). However, he does not agree with such way of thinking since domestic courts do not have law-giving power and, thus, when they apply customary law, it is presumed that such law has already been recognised as such by States themselves ((See id.)).

He then goes on to draw a distinction between morality and law, claiming that the former refers only to one’s conscience, whereas the latter, though referring to one’s conscience, will in the end have to be enforced by an external power ((See id., at 6.)). Another remark consists of the dismissal of the need of the existence of a law-giving authority to ascertain the law, since, as in the primitive societies it was the community who endorsed or rejected a rule of law without laying down guidelines, in contemporary times law can also be of unwritten and customary nature ((See id., at 7-8.)).

Based on such assumptions, Oppenheim identifies three essential characteristics of law: the existence of a community, a body of rules for human conduct and their enforcement by an external power ((See id., at 8.)). As a subsequent step, he turns to examine whether these elements are present on the international plane. As to whether there exists a universal community of States, he strives to identify the nature of a community as a body of individuals who are generally dependent upon each other through the existence of common interests ((See id., at 10.)). According to Oppenheim, a community can refer not only to individuals but also to States and the existence of an international community should not be contested, in view of the fact that the civilised States are not only interconnected by common Christian religious ideas but also by common interests in fundamental fields, such as trade, agriculture and industry ((See id., at 11.)). It should be noted that the existence of the Family of Nations is fundamental for the existence and further development of International Law, although its composition seems to be static and limited to “civilised” States of Europe and the Americas ((Kingsbury, Benedict, Legal Positivism as Normative Politics: International Society, Balance of Power and Lassa Oppenheim’s Positive International Law, 13 EJIL 401, at 409-412 (2002).)).

With regard to the second criterion, Oppenheim thinks that this can be settled with relatively no difficulty since an abundance of customary rules have been evolved, whereas written rules are more and more often created and steps have been taken towards the central organisation of the international community ((See Oppenheim, supra note 3, at 12.)). As far as the third condition is concerned, the mere inexistence of a central external authority with the mandate to enforce rules should not be considered as a defect, rather this criterion should be regarded as met since States themselves ensure the necessary enforcement through a self-help and intervention system by supporting those experiencing the effects of a rule violation ((See id., at 13-14.)). Within this context, it should be noted that the balance of power constitutes a prerequisite for the existence of International Law, since it is the mechanism through which the respect of International Law is guaranteed ((Kingsbury, supra note 15, at 16-21.)).

A basic notion within this context seems to be that of “common consent”. Once again Oppenheim starts from the community level, at which the majority of the community members by consenting on a specific legal issue at a given time create law which in turn endures time and binds next generations ((See id., at 16.)). Nevertheless, the international community’s composition does not alter so often and new States have to be admitted in the Family of Nations through recognition ((See id., at 17.)). Within this framework, the common practice that States have followed in response to a certain issue and their belief in the need for binding rules shows their consent to the creation of customary rules ((See id., at 17-18.)). According to Oppenheim, it is not necessary to prove that each State has concurred to the creation of a rule, but each one of them is to be bound by all settled rules with no possibility to deny compliance with specific rules in the future ((See id., at 18-19.)).

It should also be highlighted that, according to Oppenheim’s definition, only custom and treaties make up of the body of International Law. On the one hand, custom can be ascertained by State practice and the conviction of States that such practice is legally binding ((See id., at 22-23.)). On the other hand, the only treaties that should be taken into account when referring to International Law are those called by Oppenheim “law-making treaties”, which lay down new rules, confirm, define or abolish existing customary or other treaty rules ((See id., at 23-24.)).

In view of the overview of Oppenheim’s definition of International Law, it has been acknowledged that Oppenheim’s International Law “still is the outstanding and most frequently employed systematic treatise on the subject ((Nussbaum, Arthur, A Concise History of the Law of Nations, at 247 (1954).)),” that “the original book reveals only small traces of a national standpoint”and “its success is rather due to a clear systematic approach underlying Oppenheim’s legal theory ((Schmoeckel, Mathias, The Internationalist as a Scientist and Herald: Lassa Oppenheim, 11 EJIL 699, at 701 (2000).)).” Nevertheless, it has also been mentioned that the whole treatise relies only on very few examples of state practice, seems to simply reject arguments with regard to natural law and the empirical data is largely anecdotal ((Reisman, Michael W., Lassa Oppenheim’s Nine Lives, 19 Yale J. Int’l L. 255, at 264-265 (1994).)). Moreover, it has been pointed out that Oppenheim treats customary law as a system of clearly defined rules, whereas in reality the common law system is inherently vague ((Craven, Matthew, Fitzmaurice, Malgosia, Vogiatzi, Maria,Time, History and International Law, at 96 (2007).)).

What it could also be pointed out is that Oppenheim’s definition of International Law refers to States only, excluding the possibility for any other international actor, such as individuals and international organisations, to be bound by such body of rules. On the other hand, the rules to be observed derive only from custom and treaty law, thus, ruling out the possibility of extracting legally binding rules from other sources, such as courts judgments or soft law instruments. However, such remarks should not be considered as real defects of Oppenheim’s definition if one embarks on contextual speculations in a sense that international organisations were not a common feature of Oppenheim’s time, no rules referring specifically to individuals were present back then and no international court, as today’s International Court of Justice, existed upon whose judgments one could dwell and extract rules of law. What is certain is that Oppenheim’s treatise “gave a comprehensive, and yet detailed, overview of international law” ((Beatson& Zimmermann, supra note 1, at 586.))and constitutes one of the best introductions to International Law.

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