I can kind of see a logic in denying someone a vote in a country they’ve not lived in for 15 years. But the whole Brexit thing could have serious repercussions for British emigrants so it’s pretty scandalous that some of then don’t get to have a voice.
That said, why would you want to live somewhere for over 15 years and not want apply for citizenship (or at least, dual citizenship)? If the boot were on the other foot and we were talking about immigrants to Britain living here for 15 years without citizenship it’d be Daily Mail headline material.
(Also, I’ve only just noticed: why does immigrant have two m’s and emigrant only have one? That’s weird.)