1. The legal source defense system in trademark infringement disputes in China means that the use of the trademark involved belongs to the legal source of the defender in trademark infringement disputes. Its theoretical basis lies in "laws, administrative regulations and other circumstances stipulated by the state" in Article 32 of the Trademark Law. Specifically, if the trademark user can prove that the trademark he uses comes from legal authorization, filing, registration, etc., and has no commercial intention and malice, then he can claim that his behavior belongs to the defense of legal source. In China's trademark infringement litigation, having a legitimate source of defense can effectively protect legitimate rights and interests and reduce unnecessary costs and risks of trademark disputes.

2. In the United States, there is a defense of "antagonistic use" in trademark infringement, that is, the trademark holder already knows or should know that there will be no confusion in the trademark, and the defendant's use is in a different market or use from that of the plaintiff, so he can claim that his use behavior does not constitute trademark infringement.

3. In Germany, a trademark holder cannot infringe on others by using the trademark for non-profit purposes, which provides a guarantee for the defense of legal source in trademark infringement disputes.