For when they don't make it easy

from here and here

Supposedly you can opt out of the facial recognition just by saying so, but it's not entirely clear to me what part you're opting out of - the scan that compares your face to your biometric template, or the image collection that's used to make the template in the first place.  If it's just the scan you're opting out of then frankly that's not good enough. I don't want my likeness enrolled into a facial recognition system against my will, never mind being verified by it after the fact.