2. The principle of reciprocity;
3. The principle of estoppel;
4. The principle of the right of first use, that is, the right of defense, comes from the principle of fairness of law.
Legal basis: People's Republic of China (PRC) Patent Law.
Article 60 Where a patent is exploited without the permission of the patentee, that is, the patent right is infringed and a dispute arises, the parties concerned shall settle it through consultation; Unwilling to negotiate or failing to do so, the patentee or interested party may bring a suit in a people's court or request the administrative department for patent affairs to handle it. When the administrative department for patent affairs finds that the infringement is established, it may order the infringer to stop the infringement immediately. If a party refuses to accept the decision, he may bring a lawsuit to the people's court in accordance with the Administrative Procedure Law of the People's Republic of China within 15 days from the date of receiving the notice of handling. If the infringer fails to prosecute and stop the infringement upon expiration of the time limit, the administrative department for patent affairs may apply to the people's court for compulsory execution. At the request of the parties concerned, the administrative department for patent affairs may mediate the amount of compensation for patent infringement; If mediation fails, the parties may bring a lawsuit to the people's court in accordance with the Civil Procedure Law of People's Republic of China (PRC).
Article 61 Where a patent infringement dispute involves an invention patent of a new product manufacturing method, the unit or individual that manufactures the same product shall provide proof that its product manufacturing method is different from the patented method.
Where a patent infringement dispute involves a patent for utility model or a patent for design, the people's court or the administrative department for patent affairs may require the patentee or interested party to issue a patent evaluation report made by the patent administrative department of the State Council after searching, analyzing and evaluating the relevant utility model or design as evidence for hearing and handling the patent infringement dispute.