- Any person, other than the registered proprietor, alleging interest in a registered trademark in respect of which an application is made under rule 97 may apply on Form TM-O for leave to intervene, stating the nature of his interest, and the Registrar may refuse or grant such leave after hearing (if so required) the parties concerned, upon such conditions and terms including undertakings or conditions as to security for cost as he may deem fit to impose.