the requirement is that they must be a native English speaker ..
English is not the world official languages, there is other nationalities and people over there ! And there is many people who can speak English better than many natives English speakers. So how will you know ?
Well you are not one for starters, I know plenty of Europeans who speak better English than I do
and they would not be caught with this rule. This is an English language forum and this is my thread so I can make up my own rules, I can also change my rules if I see fit.
The key word here is "native". That technically excludes i.e. those Europeans that speak/write perfect English, as it's not their "native" language (in most cases).
It's your topic and your sMerits, so you're free to discriminate whoever you want, but if didn't intend to discriminate, maybe replace "native" with "fluent" or "proper"?