Given the fundamental principle of party autonomy in international arbitration, one can be tempted to assume that it is primarily when the parties have not chosen the substantive law governing the subject-matter of the dispute that arbitrators are called to decide, directly or indirectly, on the applicable law to parties’ right and obligations. However, conflict of laws is relevant to different aspects of the arbitration process (determination of the applicable law to the validity of the arbitration agreement, subjective and objective arbitrability, the law governing interim measures, evidence, damages, etc.). In the presence of mandatory rules, arbitrators also may be required to apply rules other than those chosen by the parties. Moreover, in the field of investment arbitration, the nature of investment treaties implies the application of standards of protection beyond the scope of the applicable law to the substance of the dispute.
Distinct from the substantive law governing the merits of the dispute, arbitrators are often called to determine the procedural law that regulates the process of the arbitration. In fact, the basic legal framework of international arbitration is determined by the content of the lex arbitri (often the law of the place of the arbitration or lex loci arbitri). However, even if the lex arbitri may play an essential role in regulating the arbitral proceeding, the application of the law of the arbitration is not “universal.” Furthermore, arbitrators might be called to apply the conflict of laws rules of the seat of the arbitration to determine the applicable law.