Lex arbitri adalah hukum yang berlaku untuk arbitrase, mencakup isu internal maupun eksternal yang terkait prosedural suatu proses arbitrase. Berdasarkan ketentuan New York Convention on The Recognition and Enforcement of Foreign Arbitral Awards 1958 (selanjutnya disebut New York Convention), kompetensi absolut untuk membatalkan suatu putusan arbitrase terletak pada pengadilan tempat kedudukan arbitrase (arbitral seat). Akibatnya, pengadilan negara selain arbitral seat tidak dapat mengadili pembatalan putusan arbitrase. Sebagai negara anggota New York Convention, Indonesia tentunya terikat pada ketentuan ini. Di Indonesia juga terdapat ketentuan dalam Reglement of de Rechtsvordering (RV) dimana hakim wajib menyatakan dirinya tidak berwenang apabila suatu perkara di luar kewenangannya. Skripsi ini bertujuan memberikan analisis mengenai penerapan lex arbitri terhadap kompetensi absolut dalam tiga perkara permohonan pembatalan putusan arbitrase internasional, yaitu Putusan Nomor : 494 / PDT.ARB/2011/PN.JKT.PST, Putusan Nomor: 631K/Pdt.Sus/2012., dan Putusan Nomor : 271 /Pdt.G/ 2010/ PN.Jkt.Pst.

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Lex arbitri is the law applicable to the arbitration, including internal issues as well as relevant external procedural an arbitration process. Based the provisions of the New York Convention on the Recognition and Enforcement of Foreign Arbitral awards 1958 (hereinafter referred to as the New York Convention), competence absolute to overturn an arbitration decision lies in court the seat of arbitration (arbitral seat).

As a result, in addition to state courts arbitral seat can not judge the cancellation of the arbitration decision. as the country members of the New York Convention, Indonesia would be bound by these terms. In Indonesia also there are provisions in the Reglement of de Rechtsvordering (RV) where the judge shall declare itself not competent when a case in beyond its authority.

This thesis aims to provide an analysis of lex implementation arbitri the absolute competence in three cases the petition cancellation of the international arbitration decision, namely Decision No. 494 / PDT.ARB / 2011 / PN.JKT.PST, Decision Number: 631K / Pdt.Sus / 2012, and Verdict Number: 271 /Pdt.G/ 2010 / PN.Jkt.Pst.