Arbitration Commission of the Peace Conference on Yugoslavia
On 20 November 1991 Lord Carrington asked: "Can the internal boundaries between Croatia and Serbia and between Bosnia and Herzegovina and Serbia be regarded as frontiers in terms of public international law?" Applying the principle of "uti possidetis juris", the commission concluded on 11 January 1992, "The boundaries between Croatia and Serbia, between Bosnia and Herzegovina and Serbia, and possibly other adjacent independent states may not be altered except by agreement freely arrived at... Except where otherwise agreed, the former boundaries become frontiers protected by international law".
Croatia–Slovenia relations
A referendum regarding the ratification of the agreement on the arbitration between Slovenia and Croatia regarding the Gulf of Piran border dispute was held in Slovenia in June 2010. Croatia and Slovenia agreed to let outside arbitrators come up with a plan to divide the Gulf in 2009 in the hopes of finding a resolution to the dispute and easing Croatia's entry to the Union. Though the parliaments in both Croatia and Slovenia ratified the agreement, the Slovene parliament additionally voted to require a public referendum on the deal. The agreement was supported by 51.54% of voters and opposed by 48.46% of voters. In October 2010, the Slovenian law on the ratification of the agreement was also unanimously recognized by the Slovenian Constitutional Court as being in accordance with the Constitution of Slovenia. The diplomatic notes about the agreement were exchanged between the Government of Slovenia and Government of Croatia on November 25, 2010. The agreement came into force on November 29, 2010.