[arien]

Spain is divided by autonomias (comunidades autonomas). You can vote wherever you're registered to vote, nowhere else. I can't vote on issues in Extremadura or Valencia because I'm not registered in there.

I understand this affects Spain as a whole, so after the vote there should be a proper discussion rather than direct secession action (IF that were the result). But this question is regional, the rest of Spain doesn't decide if they want to live in an independent Catalonia state, because they don't live in there.