From time to time, the name of an inventor may not be listed on a patent during the application, either as a result of vanity patenting or because the inventor is a contractor and not an employee, which is perceived as raising problems of “shop right.” The problem with failing to name an inventor is that this may, if intentional, render the patent invalid and unenforceable. Alternately, since joint inventors are, in principle in US law, joint owners, in a number of well-known U.S. patent cases, the defendant has approached the un-named defendant and secured a license to the patent, which the defendant then successfully raised as a defense in court.