INTRODUCTION. International arbitration is traditionally located on the periphery of legal research. The only exception is investment arbitration. Recently, however, states have started to regularly resort to it. International arbitration, thus, became able to influence the development of common law. Many of arbitration cases involve maritime law issues; unlike the International Court of Justice, arbitration courts consider problems that don’t relate to Articles 74 and 83 of the 1982 Convention on the Law of the Sea, which regulate delimitation (mechanism of compulsory dispute resolution, regime of historical waters and maritime formations, right to hot pursuit, etc.). The emerging arbitration jurisprudence, however, is ambiguous. MATERIALS AND METHODS. The present research has been conducted on the basis of arbitral awards delivered in the three most significant and controversial cases: Arctic Sunrise case, South China Sea case and Border dispute between Slovenia and Croatia; their normative basis (the 1982 Convention, arbitration agreements and customary law); scientific comments on these awards. The methodology of the research is based upon the method of critical analysis. RESEARCH RESULTS. The author concludes that the argumentation used in these awards is unsatisfactory and inconsistent with provisions of maritime law and other branches of international law. In the Award on Arctic Sunrise case of 14 August 2015 (Netherlands and Russia), the Court indicated that the detention of a foreign vessel that violated the laws on artificial installations, is legal if the hot pursuit started when the vessel was in security zone. The pursuit of a foreign ship, however, is not a security measure, since it’s carried out after committing the violation; its goal is the implementation of responsibility. Violations of laws applicable to the artificial platforms may therefore be prosecuted throughout all the exclusive economic zone. In the Awards on South China Sea case (Philippines and China) of 29 October 2015 and 12 July 2016, the Court found that the dispute did not concern delimitation, since it does not imply the intersection of claims; its conclusions, however, are directly related to delimitation as it stated that China’s maritime areas do not extend where China suggested they would extend, but elsewhere. Also the Court did not provide convincing arguments for conclusions that the dispute does not concern “historic titles” and China does not claim sovereignty in disputed areas. Finally, it did not consider whether large-scale construction could make the island suitable for living within the meaning of Art. 121 of the 1982 Convention. In the Awards on the territorial and maritime dispute of 30 June 2016 and 29 June 2017 (Slovenia and Croatia), the Court replaced the issue of violation of the arbitration agreement by the issue of its further implementation; such an opportunity, created after the replacement of arbitrators, as well as the alleged repentance of Slovenia, however, don’t exclude the fact that Slovenia violates the provisions of the agreement, essential to the accomplishment of its object or purpose. The Court also established in favor of Slovenia an area which is not envisaged by the Convention and passes in the territorial sea of Croatia – the so-called Junction Area. DISCUSSION AND CONCLUSIONS. The considered awards contain gross legal inaccuracies that impacted the outcome of the cases. They reflect the imperfection of international arbitration, manifested in selective use of evidence, absence of guarantees against procedural abuses, complexity of the mechanism enshrined in Part XV of the Convention, etc. The awards also reflect general imperfection of the institutions of the law of the sea – such as lack of clear regulation of the jurisdiction over artificial installations, serious gaps in the regimes of historical waters and sea formations, imprecision of the exemptions from the compulsory settlement mechanism, inability of the Convention to ensure a balance of interests of states in case the territorial sea is closed.