After registration, and even after becoming incontestable, a third-party can file a petition to cancel a trademark. Grounds for cancellation include the mark becoming generic; abandonment (or non-use) of the mark; that the mark is geographically deceptive; prior use by another party; and that the mark was obtained by fraud. However, incontestable trademarks are immune to cancellation for descriptiveness.
A cancellation proceeding is similar to litigation. For example, a proceeding includes a complaint, an answer, and discovery periods. Based on the pleadings, the Trademark Trial and Appeal Board determines the cancellation or non-cancellation of a trademark.