Morton Salt Co. v. G.S. Suppiger Co. 314 U.S. 488 (1942) Suppiger had a patent for a machine that made salt tablets that were widely used in the food canning industry. They sold the machines to canneries, but only if the canneries signed a contract to buy all their salt from Suppiger. That's kind of like selling someone a car with the requirement that they only buy gasoline from your gas station. Suppiger sued Morton for selling salt to their customers. Morton countersued to have the patent declared invalid. The US Supreme Court found that Suppiger could not stop Morton from selling salt. The US Supreme Court found that a patent couldn't be used to restrain competition in the marketing of unpatented items. That's known as misuse, and is contrary to public policy. The Court found that as long as Suppiger persisted in trying to restrain trade in salt, they could not get an injunction against anyone for selling or leasing the salt tablet machine. So if you misuse a patent, you lose the right to exclude others from making your invention! Basically, the Doctrine of Misuse says that while a patent grants you a monopoly, it is a limited monopoly and can't be used to restrain trade. These days, misuse rarely comes up because situations like this one would be adequately covered by anti-trust law.