Yes, the more you know about your target the more confident you become about their nationality. Though I don't think the target needs to be a specific person, it could just be an email address couldn't it? Given just an email address you could be more than 51% certain it belonged to a foreign national and start collecting their data.

Sure, you might have to tortuously stretch the legal wording here to justify collection of any particular target, but if there's one thing this Administration has proven adept at it's tortuous stretching of the law.