Patent infringement is the commission of a prohibited act with respect to a patented invention without permission from the patent holder. The US Patent Office has no jurisdiction over questions relating to infringement of patents. In examining applications for patent, no determination is made as to whether the invention sought to be patented infringes a prior patent.
Patent infringement law is defined in 35 U.S.C. 271. U.S.C means United States Code.
Some of the key laws:
(a) Except as otherwise provided in this title, whoever without authority makes, uses, offers to sell, or sells any patented invention, within the United States, or imports into the United States any patented invention during the term of the patent therefor, infringes the patent.
The terms: makes, uses, offers to sell, or sells any patented invention have been argued in court many times and because of this there is sizeable case law that defines those terms. The key point is to understand that all four of these categories apply to patent infringement.
(b) Whoever actively induces infringement of a patent shall be liable as an infringer.
Inducing Infringement refers to the situation in which an end user or consumer infringes a patent but was actively persuaded do so by a third party. The third party may not directly infringe because they never practice the method themselves, but they induce the end user to practice the method.
(c) Whoever offers to sell or sells within the United States or imports into the United States a component of a patented machine, manufacture, combination, or composition, or a material or apparatus for use in practicing a patented process, constituting a material part of the invention, knowing the same to be especially made or especially adapted for use in an infringement of such patent, and not a staple article or commodity of commerce suitable for substantial non-infringing use, shall be liable as a contributory infringer.
This one defines contributory infringement. It is possible for a foreign company to try to circumvent a U.S. patent by importing into the U.S. only a portion of the invention, with the intent of selling it to others who create a final product or process that infringes the patent. Under this doctrine of contributory infringement, the patent holder can sue the foreign company as a contributor to patent infringement.
(d) No patent owner otherwise entitled to relief for infringement or contributory infringement of a patent shall be denied relief or deemed guilty of misuse or illegal extension of the patent right by reason of his having done one or more of the following: (1) derived revenue from acts which if performed by another without his consent would constitute contributory infringement of the patent; (2) licensed or authorized another to perform acts which if performed without his consent would constitute contributory infringement of the patent; (3) sought to enforce his patent rights against infringement or contributory infringement; (4) refused to license or use any rights to the patent; or (5) conditioned the license of any rights to the patent or the sale of the patented product on the acquisition of a license to rights in another patent or purchase of a separate product, unless, in view of the circumstances, the patent owner has market power in the relevant market for the patent or patented product on which the license or sale is conditioned.
The paragraph above is further clarification of what is and is not contributory infringement. It clarifies the rights of the patent holder, pointing out that that the patent holder can still pursue contributory infringement even if he/she has a) made money from the patent, b) licensed the technology to another, or c) refused to license the technology.
(f)(1) Whoever without authority supplies or causes to be supplied in or from the United States all or a substantial portion of the components of a patented invention, where such components are uncombined in whole or in part, in such manner as to actively induce the combination of such components outside of the United States in a manner that would infringe the patent if such combination occurred within the United States, shall be liable as an infringer.
If a United States company supplies or causes to be supplied the fundamental components of a U.S. patented invention in an uncombined form and ships them overseas where they can be combined then that company can be guilty of patent infringement because they manufactured in the United States, even though they did not manufacture in complete form.
(g) Whoever without authority imports into the United States or offers to sell, sells, or uses within the United States a product which is made by a process patented in the United States shall be liable as an infringer, if the importation, offer to sell, sale, or use of the product occurs during the term of such process patent. In an action for infringement of a process patent, no remedy may be granted for infringement on account of the noncommercial use or retail sale of a product unless there is no adequate remedy under this title for infringement on account of the importation or other use, offer to sell, or sale of that product. A product which is made by a patented process will, for purposes of this title, not be considered to be so made after -(1) it is materially changed by subsequent processes; or (2) it becomes a trivial and nonessential component of another product.
If you have a process patent in the United States and a foreign company uses that process in his home country to manufacture a product, then offers to sell, sells, or uses that product in the United States then that company is an infringer. That company may be free to sell that product in many other countries in which you have no patents - but not in the United states.