A similar thing happened with the Scottish referendum. They excluded something like 20-25% of all potential voters by saying you had to be living in Scotland to vote.

It's a tricky problem though, because you'd have to define what exactly counts as "Scottish" or "Catalan" for people who don't live there. Genetics? Culture? Birthplace? Any one of those could be considered inadequate.

It's also "funny" that a illegal immigrant in Catalonia can vote but a citizen of Madrid do not have any right even if their parent are from Catalonia.

But relax, nobody is going to vote because is illegal.

If I recall corectly it was the same for the Scotish referendum.