Diego Costa, who was born, raised, went to school in and played international football for Brazil, has signed a legal document saying that he wants to play for Spain now. Hooray!
The Athletico Madrid forward has elected to play for his country of residence, having felt extremely patriotic for the last almost 6 years and because he wasn't getting a game for Brazil I mean because he's so patriotic.
Now I don't think you should have to be born somewhere to be from there, and you can feel a certain nationality having been brought up there for any length of time, but yours and your parents/grandparents national lineage is probably slightly important if we don't want international football to become like when you change all the best players' nationalities on iss 98 so they can play for Scotland. But if you've already played international football for Brazil I don't think you should be allowed to change your mind because you feel more Spanish all of a sudden.
On second thoughts, if the Barcelona first team would like to pledge allegiance to Scotland before the next Euro qualifying campaign then I may rethink my opinion on this