Regula Iuris and Its Reflections on Lex Mercatoria

Abstract

The rise of lex mercatoria is a common trend in our current legal environment. The subject attracts attention of many academics from different legal systems and academic discussions have been constantly flourishing. The core of these discussions is the roots and sources of lex mercatoria. Concerning its roots, opinions diverge on whether it stems from ius gentium or from medieval merchant law. Another related issue is whether we are facing another era of lex mercatoria with the adoption of soft laws such as UNIDROIT Principles of International Commercial Contracts. As to the sources of the ‘merchant law’, debates focus on which sources lex mercatoria do possess. In general, international conventions on commercial law, commercial customs and usages, model laws, standard contracts and general principles of law are seen as part of lex mercatoria, however different views are taken on their consideration as a source of this legal system detached from national laws. Accordingly, it should not be wrong to say that lex mercatoria is still an ambiguous concept despite its popularity. Hence, opinions vary on its applicability as an ‘anational’ legal order as well: some acclaim its detachedness from national legal systems whereas others cast doubt its existence as a separate legal order. Nevertheless, we do often come across lex mercatoria as a reference to applicable law, especially in arbitral practice. This paper aims to establish a link with regula iuris and lex mercatoria. Some legal maxims are already deemed as being a source of lex mercatoria: examples include ‘pacta sunt servanda’, ‘venire contra factum proprium nemini licet’ (prohibition of inconsistent behavior), ‘culpa in contrahendo’, ‘clausula rebus sic stantibus’ etc. Accordingly, this paper evaluates the place of these maxims in lex mercatoria practice and attempts to find out whether lex mercatoria can be also seen as a new regula iuris on international level.