Legal basis: Article 12 of the Patent Law of People's Republic of China (PRC). Any unit or individual that exploits another person's patent shall conclude an exploitation license contract with the patentee and pay the patentee the royalties. The licensee has no right to allow any unit or individual other than those stipulated in the contract to exploit the patent. Therefore, it is legal and reasonable for the patentee to ask the person who uses his patent to pay the patent license fee. If another person uses another person's patent without paying the license fee, it constitutes patent infringement.