In real estate the invasion of the boundary of a landowner's property is called trespass, while invasion of a patentee's claims is called infringement.
Patent infringement is the unauthorized use of property. When a person or business uses your patent, they trespass on your property – your "Intellectual Property” which includes copyrights, trademarks, patents, industrial design rights, and trade secrets. Under law, you have the right to pursue a civil remedy against a perpetrator of patent infringement. Both trespassing and infringements are civil wrongs or "torts." Unlike a trespass, patent infringement is a statutory wrong and is governed by federal law.
The United States Code 35 U.S.C. 271(a) defines infringement as "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 United States Code 35 U.S.C. 271(e)(2)(A) further defines an infringement as “It shall be an act of infringement to submit - as an application under section 505(j) of the Federal Food, Drug, and Cosmetic Act or described in section 505(b)(2) of such Act for a drug claimed in a patent or the use of which is claimed in a patent”. The patent infringement plaintiff is often an individual or a small business, while the patent infringement defendant is usually a large, well-financed corporation.
Infringement can be direct, indirect, or contributory. Whoever without authority makes, uses, or sells the patented invention is a direct infringer. If a person actively encourages another without authority to make, use, or sells the invention, the person persuading is liable for indirect infringement. Contributory infringement can be committed by knowingly selling or supplying an item for which the only use is in connection with a patented invention. Good faith or ignorance is no defense for direct infringement, but it may be for indirect or contributory infringement.
Patent Infringement By the Government
Patent infringement, by the Government, of privately owned patents, is governed by United States Code 28 U.S.C. 1498, which provides that a suit against the Government in the U.S. Court of Federal Claims is the exclusive remedy for patent holders who allege their patented invention has been infringed by the U.S. Government or by one acting for the Government. The primary purpose of this statute is to protect and relieve contractors from any liability for infringement by the owner when an invention is used by or manufactured for the United States. By virtue of this statute, the Government may be held liable to the patent owner for payment of the "reasonable and entire compensation" for its unauthorized use of the patent. Unlike a private party, however, the Government cannot commit the tort of "patent infringement." Governmental use of a patented invention is viewed as an eminent domain taking of a license under the patent and not as a tort.
The Government may delegate its eminent domain power over patents to contractors acting on its behalf. This is accomplished through inclusion of the "Authorization and Consent" clause in the contract [FAR clause 52.227-1]. This clause is usually included in research and development contracts and is a very significant power to grant to a contractor as it makes the Government responsible for the contractors' infringement of any patents during the course of performance of the contract; the patent owner must bring her/his action against the Government, not the contractor.