Union means a state made of distinct populations. In proper Union their is law and guidelines describing under what conditions a country can join the Union, and also under what conditions it can separate.
What were the conditions of separation in Yugoslavia?
There were no countries joined in this union. Neither Slovenes, Croatians or Bosniaks ever had the country before Yugoslavia. The only two countries that joined the Union were Serbia and Montenegro (as Kingdoms). That was in 1918. After the WW2, communist Yugoslavia was made as Union of people.
"On 31 January 1946, the new constitution of Socialist Federal Republic of Yugoslavia, modeled after the Soviet Union, established six republics, an autonomous province, and an autonomous district that were part of SR Serbia. The federal capital was Belgrade." (
source) They were not ethnic, and were never intended to be the lines of future separation, which was forbidden by the constitution. Constitution referred to peoples as a "base units" of this Union. It was not a union of administrative zones.
So for example, Macedonians had the right to claim independence, but not did Republic of Macedonia. Serbs could have claimed independence from Yugoslavia, but not republic of Serbia. EU and USA knew this, and they knew that if they recognize the independence of the administrative zone of Croatia that the war would brake up. And they did recognize it as a sovereign state of Croatia, although they had no sovereignty over that area, although the international law did not allow that, although Yugoslav constitution disallowed that, although they knew it will start a war.
The way this was done was unlawful and illegitimate from all sides and I must inform you that formally Yugoslavia still exists. EU ans USA played very dirty and disgusting part in starting the war here.
I neither referred to the war nor it could be understood from our exchange.
Besides, did you hear about Independence Wars?
Yes I've heard of Independence war, but
did you hear about the law and the democracy? You can't win an Independence war in Carolina and then claim the parts of New Zealand and Canada, just because the Crown referred to those territories under the same (for example "The colonies"), and especially not if New Zealanders and Canadians don't want to be in your "Independent country".