Having completed his studies of the law at the University of Zagreb’s Law Faculty in 1997, Dr Sosic first worked as clerk-at-law at the law office of Dr Dragutin Sikirić, attorney-at-law in Zagreb. He passed the State Judiciary Examination (Croatian equivalent of the Bar examination) in 2000. In 2001 he obtained the position of junior research assistant at the Zagreb Faculty of Law. After completion of the second university degree, i.e. master’s degree (magister scientiarum - mr.sc.), in the field of international law in 2006, he was chosen for the post of assistant at the Zagreb Law Faculty’s Department of International Law, and in 2007 was granted the teaching and examination licence for the subject International Law. In 2012 he earned a doctoral degree in the field of international law with a dissertation entitled “The Protection of the Underwater Cultural Heritage in International Law”. He became assistant professor in 2015. Dr Sosic spent research periods at the Max Planck Institute for Comparative Public Law and International Law (Max-Planck-Institut für ausländisches öffentliches Recht und Völkerrecht) in Heidelberg (Germany) and at the Asser Institute (T.M.C. Asser Instituut) at The Hague (Netherlands). He also attended courses at the Hague Academy of International Law, the Rhodes Academy of Oceans Law and Policy in Rhodes (Greece) and the Inter-University Centre in Dubrovnik (Croatia). He was part of the expert group formed by the Ministry of Foreign and European Affairs of the Republic of Croatia which prepared the legal positions of Croatia in the arbitral proceedings against the Republic of Slovenia regarding the maritime and land boundary between the two states.