The ide is based on self determination , a people should be allowed to govern itself .

 This is a a UN decree .

 So if the Tibetans so wished they could have a referendum and choose to break away from China , but China won let  them , and if they all vote din the elections there , to break away , they would still be out voted , by the hundreds of millions of Chinese .

 To remdey this situation of a smaller country never getting its views heard , they have laws of Slef - detemrination .

 In Scotland the SNP gained a majority in the Scottish parliament , and they had the referendum , in their manifesto , so they set about proposing it , the UK Govt , keen to promote democracy , agreed to this , and they called it , the Edinburgh Agreement .

 To respect the democratic result of the vote , and have clear laws (as Govern Uk Elections ) governing the referendum .

the Crimea is no doubt mostly Russian anyway , and indeed has a chequered history through the centuries .

So when threatened by the Govt in Kiev , Putin sent in troops , and got them to vote on whether they wanted to stay in Ukraine or , join Russia .

 I suppose its a s good a referendum as any , its just not recognised by the USA and her allies , though they did recognise the current govt in Ukraine very quickly , even though they had no vote there .