The expression ‘international uniform law’ indicates a set of identically worded legal rules that are binding on a general level in at least two jurisdictions where they are supposed to be interpreted and applied in the same manner. International uniform law is the result of specific efforts towards the creation of law that is intended to be the same on an international level. Where this animus unificandi is lacking, it may well be possible for the laws of different jurisdictions to be identical to each other, but they will nevertheless not constitute international uniform law. This is why, for instance, the spontaneous, unintentional creation of identically worded legal rules in different jurisdictions as an answer to similar problems arising in practice cannot amount to international uniform law. The same is true as regards the unilateral reception of foreign legal rules—although this may lead to legal rules of various jurisdictions being identical, it cannot lead to international uniform law as the newly introduced legal rules will be interpreted and applied independently from their foreign model.
Law that is simply ‘harmonized’, that is, law that has not been created with the intention of getting rid of the existing differences, but rather with the goal of merely reducing those differences (as is the case for the law originating from most EU directives) does not constitute uniform law. This does not mean that only those legal rules that fully correspond to each other can be considered uniform law. If this were the case, it would be impossible to ever speak of uniform law, as fully corresponding legal rules are very rare, even where the wording of the legal rules is identical. The reasons for divergence are manifold, such as the fact that the uniform texts are often drafted in different languages and are interpreted and applied differently in practice. Therefore, the starting point for determining whether there is uniform law is the degree of intended similarity of the legal rules in question. Where the maximum degree is intended, ie where the law is supposed to be one and the same, uniform law may exist despite any factors that may have a negative impact on the uniformity. Where, however, from the very beginning the efforts are merely aimed at the creation of a similar, harmonized law, one cannot speak of uniform law.
From what has just been said, it becomes apparent that the intended identity of the legal rules is a characteristic of uniform law. The area of law to be unified, however, is completely irrelevant for the purpose of defining the concept at hand, since ‘uniform law’ indicates not so much an area of the law as its status. Consequently, efforts towards the creation of uniform law can relate to the most disparate areas of law. They can, for instance, relate to the private international law area as well as the substantive law area. Regarding the latter, a distinction has to be made between unlimited and limited uniform substantive law.
Unlimited uniform substantive law is constituted by those legal rules that also govern purely domestic situations, which is why this kind of uniform substantive law is rather rare (still, there are a few examples, such as the rules laid down by the Convention providing a uniform law for bills of exchange and promissory notes of 7 June 1930 and the Convention providing a uniform law for cheques of 19 March 1931). Limited uniform substantive law, on the other hand, solely governs trans-border situations, that is, situations that have a relationship to more than one country. Unlike unlimited uniform substantive law, limited substantive law does not per se have an impact on domestic law. This is an advantage insofar as it allows a given state to enter a limited uniform substantive law instrument into force even where it contrasts with that state’s domestic law. This means that the adoption of limited uniform substantive law does not require a high degree of compatibility vis-à-vis the domestic substantive law. The same is true with uniform private international law because it has an impact solely at the conflict of laws level rather than the substantive one.
A high degree of compatibility is, however, a prerequisite for the success of any effort towards the creation of unlimited uniform substantive law, which is why there are areas of law in relation to which unlimited uniform substantive law will be nearly impossible. In this respect, it may suffice to mention areas such as family law and the law of succession—areas characterized by national particularities originating from nation-specific social, ideological, religious and cultural values and backgrounds which national legislatures will hardly give up. Even though limited uniform substantive law would not impact the existing national particularities in these areas, insofar as the domestic law would still apply to (purely) domestic situations, limited uniform substantive law in these areas is very rare as well since these areas are far too influenced by the aforementioned values to allow for even the creation of a limited uniform substantive law.
In the aforementioned areas, one can find, however, uniform private international law. This is due to the fact that private international law is—as much as its connecting factors—influenced to a much lesser extent than its substantive counterpart by such particularities and values. In other words, it is much easier to forego domestic private international law rules than substantive rules, since the former are rarely the expression of deeply rooted cultural, sociological, ideological or religious beliefs.
2. Aims and goals
At this point one must wonder what goals the unification of law pursues and whether the distinction between uniform substantive law and uniform private international law influences not only the possibility of unifying certain areas of law, but also has an impact on the goals of the unification process. The starting point is the realization that unification of law does not in itself constitute a goal that is to be pursued at all costs, independently from any valid justification. Instead, unification of law has to aim at more than ‘just’ obtaining unified law. The issue of which other goals may justify the unification of law depends, in part, on the area of law (such as private international or substantive law) to be unified, as the goals of unification of one area may differ from those of a different area.
Of course, efforts towards the unification of different areas of law may also pursue the same goals. For example, one of the goals behind the unification of both substantive law and private international law is to avoid the unequal treatment to which the application of different legal rules may lead in a specific instance. This does not mean, however, that in light of that common goal, the distinction between private international law and substantive law becomes irrelevant. This is due to the fact that private international law and substantive law have an impact on different levels. With respect to avoiding unequal treatment, uniform private international law guarantees that the courts of the states in which it is in force apply the same substantive law. This leads to uniformity on a conflict of laws level. Consequently, parties have (apart from the cases of dépeçage) merely to provide for the application of one substantive law. There is a downside to this: courts may well have to apply an unfamiliar law, which leads to uncertainty and costs arising from the determination of the contents of that unfamiliar (foreign) law. In any case, it should be mentioned that uniform private international law cannot prevent all unequal treatment. For example, the party whose law will be applicable will have an advantage, insofar as that party will have no difficulties nor will that party incur any costs in determining the contents of the applicable law. Uniform substantive law, on the other hand, guarantees that all parties from countries where it is in force will have equal access to the substantive law solutions, thus ‘levelling the playing field’. The fact that uniform substantive law always deals with the situations falling within its sphere of application in the same manner, while uniform private international law merely guarantees resort to the same substantive law, also avoids unequal treatment.
The goal of international uniform substantive law most often referred to is, however, a different one, namely making the application of law easier by creating a (substantive) law that, according to the prevailing view, avoids the need to resort both to private international law—considered to be rather complicated—and to the applicable law determined by means of that very same private international law. This promotes certainty of law, makes business decisions easier and facilitates risk assessment. According to the prevailing view, this leads to a reduction of costs, benefiting not only the parties involved but the economy as a whole.
Therefore, where no resort to private international law is had, an important source of uncertainty is avoided which, in turn, certainly saves costs. However, the assumption that uniform substantive law avoids the need to resort to private international law cannot be embraced. This is due in part to the fact that international uniform substantive law is not exhaustive; it does not constitute a substantive law capable of dealing with all legal issues, thus making resort to the applicable domestic law necessary. This means that private international law is indispensable, as the applicable domestic law must be determined by means of the private international law (of the forum).
In part, this is due to the fact that, at times, international uniform substantive rules themselves refer to private international law. For instance, the United Nations Convention on Contracts for the International Sale of Goods drafted by UNCITRAL (the United Nations Commission on International Trade Law), makes its applicability dependent, inter alia, on whether ‘the rules of private international law lead to the application of the law of a Contracting State’ (Art 1(1)(b)). Similarly, the UNIDROIT (International Institute for the Unification of Private Law) Convention on International Factoring applies, inter alia, when ‘both the contract of sale of goods and the factoring contract are governed by the law of a Contracting State’ (Art 2(1)(b)) (factoring).
If one also considers that at least one recent international uniform substantive law instrument, namely the 2005 UNCITRAL Convention on the Assignment of Receivables in International Trade, itself contains a set of private international law rules, it becomes even clearer that international uniform substantive law and uniform private international law are not antagonists, as the prevailing view seems to suggest, but instead must go hand in hand if overall uniformity is to be achieved.
3. Sources of international uniform law
From the definition of international uniform law proposed in 1. above, it can easily be derived that the concept is independent not only from the area of law to be unified, but also from the particular form the unification efforts may take, which is why the form these efforts take can be very heterogeneous.
Regarding the forms these unification efforts may assume, one has to first mention international agreements, such as the United Nations Convention on Contracts for the International Sale of Goods. The preference for international agreements is justified because only international agreements (independently of whether they are bi- or multilateral) are capable of achieving the level of uniformity aimed at when trying to create uniform law. This is due to the fact that the states which adopt such agreements may only adopt them as a whole. In other words, an international agreement can only be adopted tel quel, without any modifications. Moreover, the states adopting an international agreement are bound not to modify it unilaterally at a later stage. This is worth mentioning, as there are constitutions that do not expressly state that international agreements prevail over domestic law enacted at a later stage.
In some instances, the rigidity of international agreements, an advantage in those cases where a specific area of law is best governed by rules that are fully identical in at least two jurisdictions, may constitute a disadvantage. This rigidity may push a legislature not involved in the drafting process to refuse international agreement as a whole, simply because of the presence of a single provision, since the all-or-nothing principle applied to international agreements also mandates application of that single provision. This disadvantage cannot always be countered by introducing reservations, which can be found in every recent international uniform law agreement. Even though the possibility of declaring reservations may help, in that it gives legislatures some room to manoeuvre (by allowing them to avoid the application of some provisions), that possibility is generally unable to dissipate all doubts vis-à-vis the disadvantages of a given agreement.
Model laws, such as the 1985 UNCITRAL Model Law on International Commercial Arbitration, are sources of international uniform law that are much more flexible than international agreements; they are legislative texts that are recommended to states for adoption as part of their national law (with no obligation whatsoever for enactment). The flexibility that characterizes model laws (and that international agreements are missing) allows states to conform their domestic legislation to specific domestic needs and, thus, avoid the concerns that may be triggered by a unification of law based on the aforementioned all-or-nothing principle. This adaptability, which also allows states to unilaterally modify the rules enacted, promotes the willingness of states to participate in the unification efforts. It bears a risk, however: legal rules intended to create uniformity may develop differently in the various states due to their being adapted to fit different needs and situations.
The decision of which type of instrument (international agreement or model law) should be resorted to is made on a case-by-case basis and depends on various factors, most notably, but not exclusively, on the degree of unification intended to be reached. It is worth noting that the importance of this decision is reduced by the fact that international agreements can also function as models for domestic legislation.
The instruments referred to up to now—as well as the EU regulations which, in relation to the topic at hand, have mainly created uniform private international law—are all instruments of legislative unification. This type of unification of law is to be distinguished from unification of law by non-legislative means, the forms of which are as numerous as that of the legislative unification. According to various commentators, such non-legislative unification may take the form of case law or the law originating from standard contract clauses. This must be doubted, however, since these kinds of ‘laws’ lack one of the prerequisites of uniform law, namely being binding on a general level. In effect, apart from those very rare instances where the law originating from standard contract forms has become customary law, standard contract terms have to be agreed upon by the parties to be at all binding. The same is true for those rules that have been elaborated by scholars and institutions to promote international trade, such as the UNIDROIT Principles of International Commercial Contracts (see Tribunale di Padova, 11 January 2005, Riv Dir Intern Priv & Proc 791 (2005)).
Generally, case law is not binding on a general level either and therefore cannot constitute uniform law. Moreover, if one considers that courts generally apply domestic rules that do not pursue unification goals, it is even less appropriate to consider case law a source of uniform law. This, however, does not mean that courts do not have an important role to play in the unification process. Ultimately, it is up to the (domestic) courts to interpret international uniform law, ie to let identically worded legal rules (uniform law in the books) come to life (uniform law in action), at least in those very many cases where the interpretation and application of uniform texts (interpretation of international uniform law) is not left to a supra-national tribunal (such as the European Court of Justice (ECJ)). Thus, domestic courts are indispensable for the creation of uniform law.
Bernhard C H Aubin, ‘Europäisches Einheitsrecht und intereuropäische Rechtsharmonie?’ in Konrad Zweigert (ed), Europäische Zusammenarbeit im Rechtswesen (1955) 45 ff; René David, ‘The International Unification of Private Law’ in IECL II (1971) ch 5; Jan Kropholler, Internationales Einheitsrecht: Allgemeine Lehren (1975); Thomas Weismer, Grundfragen grenzüberschreitender Rechtsetzung (1995); Jürgen Basedow, ‘Worldwide harmonisation of private law and regional economic integration— general report’  Uniform Law Review 31; Urs Peter Gruber, Methoden des internationalen Einheitsrechts (2004); Gudrun Schmid, Einheitliche Anwendung von internationalem Einheitsrecht (2004); Marco Torsello, Common Features of Uniform Commercial Law Conventions (2004); Karin Linhart, Internationales Einheitsrecht und einheitliche Auslegung (2005); Louis Marquis, International Uniform Commercial Law: Towards a Progressive Consciousness (2005).