Slovenia was able to declare its secession from yugoslavia and its independence in 1991 with little opposition from yugoslavia for all of the following reasons, except

On June 25, 1991 Slovenia declared independence. The very next day, the newly-formed state was attacked by the Yugoslav Army. After a ten day war a truce was called and in October 1991 the last soldiers of the Yugoslav Army left. So there was opposition from Yugoslavia 

I posted it here, but the answer came from -SueAnn Arnold