General Principles of Law
by Axel Metzger
General principles of law (allgemeine Rechtsgrundsätze, principes généraux) are a source of law of particular importance in European private law. Since the 1950s, the European Court of Justice has invoked general principles of law to fill gaps in, and interpret, Union law. Article 340 of the TFEU explicitly refers to ‘the general principles common to the laws of the Member States’ as governing the non-contractual liability of the European Union. However it is not only in this specific area that the ECJ has invoked such general principles, but also in all fields of EU law. In addition, academic projects commenced in the 1980s to determine ‘Principles’ of European law on a comparative law basis. The oldest of these working groups, the Commission on European Contract Law, which finished its work with the publication of the third part of the Principles of European Contract Law (PECL), is a noteworthy example. In recent years, other projects on tort and family law and on trusts and insurance law have followed. On the international level, the UNIDROIT Principles of International Commercial Contracts (PICC) are of central importance. However, case law of the ECJ and ‘Principles’ projects are only sub-areas of the whole field of the scope of application of general principles of law in European private law. General principles also play an important role within the national private law systems and at the level of international law.
There are many different theories regarding the general principles of law. According to a common theory, especially in continental jurisdictions, a general principle is defined as a basic legal norm that may be derived by analogia iuris from the single statutory provisions of a given legal order. Other theories emphasize the tendency of general principles of law to transcend geographical and temporal borders. These definitions rely on the characteristics of general principles shared by different jurisdictions or legal systems of different eras. Another widely held approach emphasizes the character of general principles of law as intermediaries between law and morality or other extralegal standards. In the last decades, the international discussion among legal theorists has mainly focused on Dworkin’s distinction between ‘rules’ and ‘principles’. Under this approach, rules are legal standards that work in an ‘all-or-nothing fashion’, whereas principles have a ‘dimension of weight’. However, it is doubtful whether this distinction is the most appropriate for delineating principles and rules in private law. There are other criteria, in particular the derivation of the principle, by which a principle might be more substantially differentiated from other types of legal norms. Moreover, compared to the commonly used notion of the general principle in the area of private law, the distinction between principles and rules as proposed by Dworkin seems rather artificial.
The following definition provides a synthesis of the key elements of the different theories: A general principle of law is a legal standard that is derived from legal rules by way of inductive generalization. The sources for this process of induction may be taken from the same legal system. This is the case when European courts infer general principles from specific rules of the acquis communautaire. The same method is applied by the courts of civil law countries when using multiple rules within the civil codes to establish general principles. It can also be found in common law courts when general principles are inferred from single instances in the case law. But the sources of general principles may also be taken from other legal systems. The generalization is then one across different legal systems. ‘General’ in this case refers to ‘internationally accepted’. This concept is at the core of the ECJ’s method of deriving general principles from the Member States’ legal systems. Finally, general principles may also be taken from historic legal norms; the generalization in this case is over time. In all cases the general principle is defined as the outcome of an inductive generalization from the underlying sources. The definition does not cover each and every use of the notion ‘principle’ in common legal parlance. In particular, the basic norms of the Civil Codes, eg Art 1382 of the French Code civil (‘Any act whatever of man, which causes damage to another, obliges the one by whose fault it occurred, to compensate it.’) or § 812 of the German Bürgerliches Gesetzbuch (BGB) (‘A person who obtains something as a result of the performance of another person or otherwise at his expense without legal grounds for doing so is under a duty to make restitution to him.’), are not principles in the sense of the definition used here.
2. Historical perspective
General principles of law are not an invention of modern times. The Digest of Justinian (D. 50. 17.1) (Corpus Juris Civilis) contains a famous fragment from the classical period which deals with some of the methodological problems raised by the induction of principles from sources. It is therefore not surprising that the origins and functions of maxims, regula iuris and other forms of generalization from Roman case law are well-established today.
Another source, in Roman law, for today’s general principles of European private law may be found in the jurisdiction of the praetor peregrinus, who in cases of Romans and foreigners did not apply the ius civile, but the ius gentium which was assumed to be based on the general principles common to all people. Today, legal historians are convinced that the ius gentium was not based on any comparative law analysis but was used as a vehicle for the application of the ius civile principles freed from the strict formalities of the ius civile. Therefore, a comparison of the Roman ius gentium with today’s developments regarding European or transnational principles should be carried out with caution. The same is true for any analogy to the medieval philosophy of Christian natural law (Thomas Aquinas) or later natural law theories (Hugo Grotius). References to ‘general principles’ in different natural law theories were used to support or correct the sources of positive law in the light of a lex divina or a law of reason.
Of particular interest is the comparison of today’s developments in European private law with legal developments at the eve of the codification movement in continental Europe beginning in the 17th and 18th centuries, especially in France. The function of general principles in both situations are remarkably similar, since multiple local laws need(ed) to be harmonized in an emerging integrated economic area. In France, this required preparatory works by legal scholars aimed at drafting a Droit commun de la France in the form of general principles of law. These preparatory works served later as the basis for the drafting of the Code civil.
Today, three types of principles of European private law can be distinguished. The first type of principle is inferred from rules of only one legal order. In this case, the scope of application of one or several rules of a given legal order is extended. Typically, the induction of general principles is achieved by way of analogia iuris, in which a principle is derived as a common denominator of several statutory or case law rules and recognized as an independent legal norm. The second type is characterized by the use of comparative law to derive general principles; here rules of other jurisdictions—be they from a federal system or from the international level—are used in deriving a general principle that is used afterwards internally or in a multistate setting. The third type of principle is derived from historical legal rules; in this group maxims or other historical legal rules are elevated to the level of principles applied in the same jurisdiction or invoked at an international law level.
General principles are sometimes, as a matter of course, based on different sources, eg on the basis of internal induction and historical rules which have inspired the legislature or on the basis of comparative law and common historical roots of the compared jurisdictions. However this possible mix of sources does not make the suggested typology superfluous because it is possible to find pure examples of each type.
4. Recognition of general principles in legal practice
The different types of general principles of law may be found on all levels of the European multi-level system. However, they are of differing significance at the various levels.
a) National level
At the national level of each EU Member State, a general principle derived exclusively from internal sources of the jurisdiction in question remains of foremost importance. An example from German law is the principle of liability for apparent legal positions (Rechtssscheinhaftung). The principle is mainly derived from §§ 171 and 172 Bürgerliches Gesetzbuch (BGB) (liability of the principal for an apparent agent in specific cases) and § 405 (protection for the assignee if a transferred claim does not exist or cannot be transferred). Courts have referred to the principle in other cases of apparent authority of agents, assignment chains or the transfer of mortgages.
Inferring general principles from single instances is not unique to continental legal reasoning. A similar method is applied in English common law. A classical example is the House of Lords’ decision in Donoghue v Stevenson (1932) AC 562 in which the court inferred from single cases of tort liability the general ‘tort of negligence’ which is today recognized as an independent ground for liability. Although from an epistemological perspective the reasoning is similar to that of continental lawyers, one should keep in mind that English judges are rather reluctant to create broad general principles of law and are even more reluctant to use such principles as constructional elements of a legal system.
Of far less significance at the national level are general principles based on a comparative law analysis. The courts of the Member States rarely refer to arguments based on comparative law. References to internationally accepted principles are even less frequent. However, there are examples of such references, especially in smaller jurisdictions with less internal material from which principles may be derived, eg Austria and the Netherlands. Also, the English courts have kept their tradition of comparing English law with the law of other common law jurisdictions.
Finally, in the continental jurisdictions, reference to general principles of law may constitute reference back to older concepts of law which have been formally abandoned. An example is provided by the French law of prescription. The French Code civil enumerates a number of specific cases in which the limitation period operates. Article 2251 Code civil states that a suspension of limitation is only granted in cases that are expressly provided for under statute. The French Supreme Court nevertheless recognizes additional cases of suspension based on the ‘principle’ contra non valentem agere non currit praescriptio (prescription does not run against a person who is unable to act).
b) Union law level
At the level of Union law, two types of principles of EU law can be distinguished, those inferred from EU legislation and those inferred from the laws of the Member States. An example of the first type is provided by ECJ competition law. In ECJ Case 17/74 – Transocean Marine Paint  ECR I-1063, the ECJ recognized the right to be heard as a general principle of EU competition law and referred to Arts 2 and 4 of Reg 99/63, regarding antitrust procedure, as more specific expressions of the underlying principle. The ECJ has so far been very reluctant to derive any underlying general principles from the many European directives in the field of private law. By contrast, European legal scholars have begun to ascertain principles based on the acquis communautaire, including directives. The Acquis Principles provide an important example for the field of contract law.
From the outset, the ECJ has based its decisions on general principles derived from the law of the Member States. Some of the main structural principles of the Union have been justified by such a comparative law analysis, eg the recognition of human rights as part of the Union’s law in ECJ Case 11/70 – Internationale Handelsgesellschaft  ECR 1125, or the non-contractual liability of the Member States in ECJ Case C-6/90 – Francovich  ECR I-5357. Occasionally, the European courts refer to international conventions ratified by Member States of the Union as a common standard. This line of argument has been employed on a regular basis regarding human rights with respect to the ECHR. But there are also examples in the field of private law in which the courts have made reference to the CISG or other treaties to support their comparative law analysis. Finally, the ECJ occasionally refers to Roman maxims and applies such maxims as general principles of law, see eg ECJ Case 23/68 – Klomp  ECR 43. Since Roman law is not historical law of the Union but older law of many Member States, this justification of general principles may be seen as a subcategory of the comparative law type.
c) International law, uniform law, lex mercatoria
General principles based on a comparative law analysis have a long tradition in international public law. This approach is codified in Art 38 of the Statute of the International Court of Justice. In public international law, general principles are substantially derived from the legal rules applicable in foro domestico of the states and then elevated to the level of international law. Many of the guiding principles of public international law have their roots in common private law principles. Pacta sunt servanda, good faith, the doctrines of breach of contract and mistake, damages, restitution and prescription are used in the law of international treaties and in other fields of public international law.
In uniform law treaties in the field of private law, such as the CISG, general principles of law play a different role. For international treaties on uniform private law rules, it is not obvious that gaps in treaties have to be filled by autonomous principles at the level of uniform law since it is also possible, as an alternative, to refer to the national law applicable under the conflicts rules of the forum. Modern conventions adopt a solution which strikes a balance between these two alternatives. Article 7(2) of the CISG and other more recent uniform law treaties state that ‘questions concerning matters governed by this convention which are not expressly settled in it are to be settled in conformity with the general principles on which it is based or, in the absence of such principles, in conformity with the law applicable by virtue of the rules of private international law’. This approach leads to the primacy of principles inferred from the Convention, whereas principles based on a comparative law analysis are of less importance.
Another field of application of the UNIDROIT PICC and other general principles of the comparative law type is international arbitration. During the last years, references to the UNIDROIT PICC have increased in arbitral awards, both as part of the applicable lex mercatoria and for interpreting or gap-filling vis-à-vis the applicable national law or international treaty.
5. Process of inductive generalization
The inductive process of inferring general principles from specific rules is the main characteristic of the principle as defined above. Reasoning by induction has been a common scientific technique since ancient times. However, it is far more than a scientific method of reasoning. It is the way in which human beings organize their experience and develop guidelines for their behaviour. Although induction is one of the major issues in traditional epistemology, philosophers have not yet presented a widely accepted theory about the logic of induction. The theoretical discussion of inductive reasoning can be traced back at least to Francis Bacon (Novum Organum, 1620) and David Hume (Treatise on Human Nature, 1739). Inductive reasoning has also been a focal point of discussion for modern epistemology (Karl Popper, Logik der Forschung, 1934; Rudolf Carnap, Logical Foundations of Probability, 1950). Some of the main arguments from the epistemological debate may be used in legal reasoning: (1) General principles derived by inductive generalization should not be regarded as absolutely valid for all unprovided-for cases. There is no principle immune to exceptions or counter-arguments. (2) Inductive inference in law does not merely rely on a basis of legal rules, but also on additional, often extra-legal premises. These premises will often constitute moral or other extra-legal standards. However, it is also possible to use very general rules, especially constitutional standards, fundamental freedoms etc as such additional premises. These premises must be made explicit. (3) Inductive inference in law does not depend on a very high number of special rules (or jurisdictions in case of a comparative law analysis) that serve as a basis. Induction can also focus on the similarities and differences between a smaller number of sources. The rational force of such a ‘variative induction’ depends on a detailed comparison of the relevant elements of the sources.
6. Legal validity
As a matter of fact, not every general principle one might derive from a rule has to be automatically qualified as binding law. Otherwise, every speculation made in scholarship, with some support in existing rules, could claim recognition as binding law. Therefore it should be accepted that a principle derived from rules can only be considered a truly ‘legal’ principle if it is recognized in legal practice, such recognition being shown either by parties who conform their behaviour to the principle or courts who enforce it by their judgments. Principles lacking any actual recognition may be thoughtful and reasonable suggestions by scholarship, but they have not (yet) entered the realm of law. Taken together with the requirements from the definition, a standard should be considered to be a ‘legal principle’ under two conditions: first, if it can be derived from the rules of positive law by way of induction, implying that it finds sufficient institutional support in the sources, and, secondly, if it is recognized as a principle by legal practice.
Obviously, this concept of legal validity is most suitable for principles derived from sources taken from the same jurisdiction. From a classical legal positivist point of view it might still be acceptable to broaden the concept of law slightly so as to comprise rules and principles inferred from state-made rules of law. It is not surprising that principles inferred by internal induction are more often accepted as legally binding than other types of principles. However, principles based on a comparative law analysis or on sources from legal history, eg Roman law, must not be excluded from the realm of law. For these principles the lack of institutional support may be replaced by additional empirical support, which is the experience of other jurisdictions or of history.
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