In Mosler Safe and Lock Company v. Mosler, the United States Supreme Court was asked to decide whether a patentee could sue a third party for infringement of a patent. The case involved a dispute between the Mosler Safe and Lock Company and its former employee, Jacob Mosler. Mosler had been employed by the company to design and manufacture safes and locks. After leaving the company, Mosler began manufacturing and selling safes and locks that were similar to those he had designed while employed by the company. The company sued Mosler for patent infringement, claiming that he had infringed upon their patent. The Supreme Court held that a patentee could sue a third party for infringement of a patent. The Court reasoned that the patentee had the exclusive right to make, use, and sell the patented invention, and that any third party who infringed upon that right could be held liable for damages. The Court also held that the patentee was not required to prove that the third party had knowledge of the patent in order to establish infringement. The Court concluded that the patentee had the right to sue a third party for infringement of a patent, and that the patentee was not required to prove that the third party had knowledge of the patent in order to establish infringement.

In Mosler Safe and Lock Company v. Mosler, the Supreme Court was asked to decide whether a trademark could be transferred from one company to another without any written agreement or assignment of rights. The majority opinion held that such an assignment was not necessary in order for the transfer of a trademark to take place. However, Justice Field dissented on this point, arguing that it would be unfair for trademarks to pass from one party to another without some form of written agreement or consent between them. He argued that if there were no requirement for an assignment document then companies would have no way of knowing who owned what trademarks and thus could not protect their own interests when using those marks commercially. Furthermore, he argued that allowing such transfers without documentation would open up opportunities for fraud as unscrupulous parties might try and claim ownership over someone else's mark with little evidence other than their word alone.