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".
Aleksandar Vučić
During 2015 and 2016, relations between Croatia and Serbia were further affected by to the ongoing migrant crisis, when Croatia decided to close its border with Serbia. In September 2015, Croatia barred all cargo traffic from Serbia, due to the migrant influx coming from Serbia in a move which further eroded the fragile relations between the two countries. 
In response to these actions, Vučić announced that counter measures will be enacted if an agreement with Croatia is not reached. 
The dispute was eventually resolved through the mediation of the EU Commission, yet the relations between the two neighboring countries remain fragile. 
On March 31, 2016, Vojislav Seselj, leader of the Serbian Radical Party, was acquitted of War Crime charges in the Hague Tribunal for Former Yugoslavia. The verdict has caused controversy in Croatia. Vučić distanced himself from Šešelj and his policy, but stated that the verdict should not be used as a tool for political pressure on Serbia.