Legal Effect

A patent provides the right to exclude others from making, using, selling, offering for sale, or importing the patented invention for the term of the patent, usually 20 years from the filing date. A patent is, in effect, a limited property right that the government offers to inventors in exchange for their agreement to share the details of their inventions with the public. Like any other property right, it may be sold, licensed, mortgaged, assigned or transferred, given away, or simply abandoned.

In order to obtain a patent, an applicant must provide a written description of his or her invention in sufficient detail for a person skilled in the art to make and use the invention. This written description is provided in what is known as the patent specification, which often is accompanied by figures that show how the invention is made and how it operates. In addition, at the end of the specification, the applicant must provide the patent office with one or more claims that distinctly point out what the applicant regards as his or her invention. A claim, unlike the body of the specification, is a description designed to provide the public with notice of precisely what the patent owner has a right to exclude others from making, using, or selling. Claims are often analogized to a deed or other instrument that, in the context of real property, sets the metes and bounds of an owner's right to exclude. The claims define what a patent covers or does not cover. A single patent may contain numerous claims, each of which is regarded as a distinct invention.

In order for a patent to be granted, that is to take legal effect, the patent application must meet the requirements of the national law related to patentability.

A patent is an exclusionary right. It gives the patent owner the right to exclude others from infringing the patent. That does not, however, necessarily give the owner of the patent the right to exploit the patent. For example, many inventions are improvements of prior inventions which may still be covered by someone else's patent. If an inventor takes an existing patented mouse trap design, adds a new feature to make an improved mouse trap, and obtains a patent on the improvement, he or she can only legally build his or her improved mouse trap with permission from the patent holder of the original mouse trap, assuming the original patent is still in force. On the other hand, the owner of the improved mouse trap can exclude the original patent owner from using the improvement.

Patents can generally only be enforced through civil lawsuits (for example, for a US patent, by an action for patent infringement in a United States federal court), although some territories (such as France and Austria) have criminal penalties for wanton infringement. Typically, the patent owner will seek monetary compensation for past infringement, and will seek an injunction prohibiting the defendant from engaging in future acts of infringement. In order to prove infringement, the patent owner must establish that the accused infringer practices all of the requirements of at least one of the claims of the patent (noting that in many jurisdictions the protection may not be limited to what is literally stated in the claims, for example due to the "doctrine of equivalents").

An important limitation on the ability of a patent owner to successfully assert his or her patent in civil litigation is the accused infringer's right to challenge the validity of that patent. Civil courts hearing patent cases can and often do declare patents invalid. The grounds on which a patent can be found invalid are set out in the relevant patent legislation and vary between countries. Often, the grounds are a sub-set of the requirements for patentability in the relevant country.

The vast majority of patent rights, however, are not determined through litigation, but are resolved privately through patent licensing. Patent licensing agreements are effectively contracts in which the patent owner (the licensor) agrees not to sue the licensee for infringement of the licensor's patent rights, usually in return for a royalty or other payment. It is not uncommon for companies engaged in complex technical fields to enter into dozens of license agreements associated with the production of a single product. Moreover, it is equally common for competitors in such fields to license patents to each other under cross-licensing agreements in order to gain access to each other's patents. A cross license agreement could be highly desirable to the mouse trap developers discussed above, for example, because it would permit both parties to profit off each other's inventions.