Failure to defend a trademark invalidation can be appealed. The Trademark Law stipulates that when the Trademark Office makes a decision to declare a registered trademark invalid, it shall notify the party concerned in writing. If the party concerned is dissatisfied with the decision of the Trademark Office, he may apply to the Trademark Review and Adjudication Board for review within fifteen days from the date of receipt of the notice. The Trademark Review and Adjudication Board shall make a decision within nine months from the date of receipt of the application and notify the parties in writing. If there are special circumstances that require an extension, it can be extended for three months with the approval of the industrial and commercial administration department of the State Council. If the party concerned is dissatisfied with the decision of the Trademark Review and Adjudication Board, it may file a lawsuit with the People's Court within thirty days from the date of receipt of the notice. If other units or individuals request the Trademark Review and Adjudication Board to declare a registered trademark invalid, the Trademark Review and Adjudication Board shall, after receiving the application, notify the relevant parties in writing and file a reply within a time limit. The Trademark Review and Adjudication Board shall make a ruling to maintain the registered trademark or declare the registered trademark invalid within nine months from the date of receipt of the application, and notify the parties in writing. If there are special circumstances that require an extension, it can be extended for three months with the approval of the industrial and commercial administration department of the State Council. If the party concerned is dissatisfied with the ruling of the Trademark Review and Adjudication Board, it may file a lawsuit with the People's Court within thirty days from the date of receipt of the notice. The people's court shall notify the other party in the trademark adjudication procedure to participate in the litigation as a third party.