In my opinion, “native speaker” should mean “a person who is completely fluent in a language and formulates their thoughts in it.” But I’m wondering if we should include “social norms” in the definition of “native”...

I did not speak English until we moved to America when I was 12. Now I hardly have a chance to speak my “native” language anymore, and instead am fluent, accent-less and conduct my daily activities (and even dream) almost exclusively in English. My kids and my wife all speak English only. I have become a native speaker, and by my own definition, I have become a foreign speaker in the language I learned as a kid. I’m still fluent in it, but I struggle sometimes to find the right words (translate from English).

Another anecdote, my wife, who is an Australian native - speaking what is closer to the “Queen’s English” than American English - was forced to take an ESL test when she first moved here to start college to assess her English knowledge. Is she a native speaker? Linguistically, yes. But she struggled to understand others in America and, more importantly, have others understand her. “Can I have some cutlery?” directed at a waiter for met with a blank stare (clearly unfamiliar with that term, I interjected with “eating utensils”). This is where societal norms and cultural lingo comes into play.