interference

In a legal setting, interference is wrongful conduct that prevents or disturbs another in the performance of their usual activities, in the conduct of their business or contractual relations, or in the enjoyment of their full legal rights. Interference can arise in a variety of legal fields including, but not limited to: tort, property, contract, business, election, patent, family, employment, and criminal law. Interference claims often arise from an intersection between tort law and another field of law.

Tortious interference is a common law tort allowing a claim for damages against a defendant who wrongfully interferes with the plaintiff's contractual or business relationships.

Property Law: Interference in the context of property law can have several applications. Unlawful interference with another individual’s piece of property may carry civil or even criminal penalties. One example is the crime of trespass, which may result in civil liability and, depending on the circumstances and applicable law, criminal penalties. Interference may also occur when a person unlawfully prevents or substantially disrupts another’s lawful use and enjoyment of their property.

Contract Law: At common law, intentional interference with contractual relations may hold a defendant liable to pay damages for intentionally and improperly interfering with a plaintiff's contractual relations with a third party. In an intentional interference claim, the burden is on the plaintiff to prove the elements of the claim rather than on the defendant to prove that its acts were justified. In United Truck Leasing Corp. v. Geltman, 406 Mass. 811 (1990) the Supreme Judicial Court of Massachusetts held that the plaintiff must prove four elements:

  • A valid contract existed,
  • The defendant had knowledge of the contract,
  • The defendant acted intentionally and improperly, and  
  • The plaintiff was injured by the defendant’s actions.

Business Law: The case International News Service (INS) v. Associated Press (AP), 248 U.S. 215 (1918) provides a good example of interference arising in a business law context. Here, the U.S. Supreme Court held that the INS practice of copying news gathered by AP from bulletin boards and early editions and then redistributing that information to its own customers constituted unlawful interference with AP’s business and was, therefore, unfair competition.

Election Law: Election interference may refer to electoral fraud, vote buying (when a political party or candidate distributes money to a voter with the expectation that they will vote for them), voter impersonation (when an eligible voter votes more than once or a non-eligible voter votes under the name of an eligible one), or foreign electoral interference (attempts by governments to influence elections in another country).

Patent Law: In patent law, interference designates a collision between rights claimed or granted; that is, where a person claims a patent for the whole or any integral part of the ground already covered by an existing or pending patent. Strictly speaking, an “interference” is declared to exist by the patent office whenever it is that two pending applications (or a patent and a pending application), in their claims or essence, cover the same discovery or invention, as illustrated in the case of Lowrey v. Cowles Electric Smelting.

Family Law: In family law, interference may arise from actions that disrupt the custodial or visitation rights of parents or guardians. For example, one parent preventing the other parent from having access to their child or attempting to alienate the child from the other parent. Another example may be one individual interfering in an attempt to carry out a decedent’s wishes, as in the case of Eugene Sonnier, II v. The Catholic Foundation of the Diocese of Lafayette, et al. 

Employment Law: Interference may arise in the context of employment law, such as interference with employment contracts or interference with labor rights. For instance, an employer interfering with an employee's right to join a labor union or engage in protected activities under labor laws. Legal protections are in place to safeguard employees from such interference.

Criminal Law: Unlawful interference may also carry criminal penalties in the context of criminal law when an individual or entity interferes with “the course of justice” (obstruction of justice) by actions such as committing perjury or purposefully hindering law enforcement in an investigation.

[Last reviewed in September of 2026 by the Wex Definitions Team]

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