411. Covenants.

Ordinary conveyancing practice assumes that there is no implied covenant by a licensor of a patent1 that manufacture under his patent will not constitute an infringement of any other patent, but express covenants to this effect are not unusual in international agreements2. A covenant by the proprietor of a patent by all means in his power to protect and defend a patent from infringement implies a covenant to pay renewal fees3. Where there is a covenant for quiet enjoyment, an exclusive licensee4 can call upon the proprietor to restrain infringement5. No covenant that the licensed patents are valid will