The U.S. Patent & Trademark Office may only decide issues of registratbility.  In other words, it only has the last word as to whether a trademark owner’s mark should be registered on the Federal Register.  The U.S. Patent & Trademark Office has no jurisdiction over common law use.  If you wish to bring an opposition or cancellation proceeding in the Trademark Trial and Appeal Board (the TTAB is the federal administrative court of the USPTO) and that proceeding ultimately settles, be sure to write in issues of use into the settlement agreement.  If your concern is solely over use of the mark, you’ll need to institute a proceeding in the Federal courts, as the USPTO does not decide issues of use.