If so, how would I go about doing this?
I am unsure what you mean by "unauthorizing" a tag. Generally speaking, any reader can read any tag as long as they share the same frequency and air-interface protocol (the "language" that tags and readers use to communicate). The latest passive ultrahigh-frequency (UHF) RFID chips support cryptographic authentication, to confirm that a tag is actually the one put on it by the manufacturer, and thus not a cloned tag.
If a reader interrogates a tag and does not receive the appropriate cryptographic response, the device will convey that information to a back-end system. What the back-end system does with that information is up to the company involved. It could send an alert to a worker, for instance, to find the item in questions and remove it from circulation, and to then investigate how the item came into the company's possession. But any tag that fails to give the proper cryptographic response during the authentication process is, by definition, an unauthorized tag.
—Mark Roberti, Founder and Editor, RFID Journal
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