where do you abandon a country?

A church doorstep? An adoption agency?
So let me give you some context... i went on vacation last week (oh glorious vacation). .. to Seattle and then to Vancouver, BC. As you know when entering a new country one must go through customs and immigration. Canada is no exception.
Now you may or may not know that I was born in Canada but carry a European Union passport as my parents are British - hence I get passport travel privileges. So the chap at the desk asked the usual questions about duration of visit, where you going, staying, etc. Then he asked me about when the last time i was in Canada - i say a few years - and ever so foolishly comment, i was born in Canada - which is obvious FYI as it says on my passport i was born in you guessed it - Canada. The incredibly serious chap behind the desk then looks at me and asked "Have you abandoned Canada"?
Excuse me?
Did you just ask me if i had abandoned a country?
yes, yes he did.
i pondered it for moment as this could be a trick question.
Of course, i said 'no'.
And he allowed me to enter Canada - oh the fool...

so since then i've been asking myself... how does one abandon a country?

i don't know how i could abandon a country - but according to the government chap you can.

who knew?

i didn't.

did you?