legal ground
Article 17 of the Trademark Law of People's Republic of China (PRC)
If a foreigner or foreign enterprise applies for trademark registration in China, it shall do so in accordance with the agreement signed between the country to which it belongs and People's Republic of China (PRC) or the international treaties to which it is a party, or in accordance with the principle of reciprocity.
Article 18
An application for trademark registration or other trademark matters may be handled by itself or by entrusting a legally established trademark agency.
If a foreigner or foreign enterprise applies for trademark registration and handles other trademark matters in China, it shall entrust a legally established trademark agency to handle it.