On October 3rd 2003, the Republic of Croatia adopted the Decision on Extension of Jurisdiction in the Adriatic Sea and proclaimed a Ecological and Fisheries Protection Zone – ZERP, beyond the borders of its territorial sea. This final paper explains the historical circumstances and the reason why ZERP was proclaimed, and not the Economic Zone as defined by the 1982 UN Convention on the Law of the Sea. An Economic Zone is an area beyond the boundaries of territorial sea which is to be declared by the coastal State and not exceeding 200 nautical miles in length from the baselines. In the area of the Economic Zone, the coastal state has no sovereignty, but enjoys sovereign rights for the exploration and exploitation, conservation and management of the natural resources of the sea located on the seabed, subsoil and in the water column. The ZERP entail a sea zone in the Adriatic Sea from the outer border of the Croatian territorial sea in the direction of the open sea to its outer border determined by general international law, and provisionally follows the line of demarcation of the continental shelf established by the Agreement between the SFRY and Italy on the demarcation of the continental shelf of 1968. Shortly after the adoption of the Decision, the application of the ZERP regime for member States of the European Union was delayed pending the conclusion of a fisheries partnership agreement between the European Union and the Republic of Croatia.