Does the lex mercatoria exist? Case law and arbitral award analysis of whether customary law in international commerce is accepted (considering different jurisdictions and legislative instruments from US, UK, and Ireland).

The thesis examines the existence, use and legal acceptance of the lex mercatoria, the so-called law of merchants, as a source of law in international commercial arbitration. In a comparative legal system including the United Kingdom, the United States and Ireland, the researcher analyses whether the lex mercatoria represents a functional transnational legal order or just a soft law with little practical authority. A doctrinal and comparative approach is adopted, in which the author will examine regulations, arbitral awards and judicial decisions, as well as doctrinal commentaries and soft law instruments such as the UNIDROIT Principles and TransLex. Chapter 4 assesses the interaction between the arbitration laws, case law and legal culture of each jurisdiction with non-state norms. Chapter 5 examines the most important arbitral awards and judicial decisions in order to reveal trends in the use and application of the lex mercatoria. Chapter 6 provides a critical assessment of the lex mercatoria with respect to exceeding the criteria of a legal system and discusses the arbitrator’s discretion and the parties’ autonomy in its application. The results show that, although arbitral tribunals are increasingly open to the lex mercatoria, national courts tend to be more conservative, concerned with issues of legal certainty and public order. This is an online research that contributes to the debate on legal pluralism and international arbitration by showing that lex mercatoria represents an intermediate source of law, supported by arbitral flexibility, maintained by party autonomy, but ultimately limited by the regulation of national courts. The research suggests that further clarifications on legal instruments should be adopted to increase their validity and utility.