Hello @TheArcUS,
Thank you for reaching out to us about this. The system is actually designed to do this already. When a contact unsubscribes, they cannot be reimported, unless they manually resubscribe. If this isn't what you're seeing, please email us at social_support(at)constantcontact(dot)com with your username, an example of a contact this happened with, and a reference to this post, so that we can research this further.
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