It was ok for Kosovo, so why not Crimea

The 2008 Kosovo declaration of independence was adopted on 17 February 2008 by the Assembly of Kosovo. The participants unanimously declared Kosovo to be independent from Serbia, while all 11 representatives of the Serb minority boycotted the proceedings. It was the second declaration of independence by Kosovo's Albanian-majority political institutions, the first was proclaimed on 7 September 1990.

The legality of the declaration and whether it was an act of the Assembly has been disputed. Serbia sought international validation and support for its stance that the declaration was illegal, and in October 2008 requested an advisory opinion from the International Court of Justice..

The Court determined that the declaration did not violate international law.

So, why not Crimea?

United Nations Security Council Resolution 1244

UPDATE:

also see Mayotte an island off the coast of southern Africa, which is the newest region of the European Union and has EU protection in international law through the provisions of the Lisbon Treaty as of 1 January 2014.