In the context of criminal trespass, "contractual interest," refers to the right to be present on another's property, arising out of an agreement between at least two parties that create an obligation to do or not to do a particular thing.
Lack of a contractual interest in the property is a material element the state must prove to convict a person of criminal trespass.[ Woods v. State, 703 N.E.2d 1115 (Ind. Ct. App. 1998)]
Example of a state statute (Indiana) discussing the term.
According to Ind. Code § 35-43-2-2(a) (1)(2) if any person who does not have a contractual interest in the property, enters the real property of another person after having been denied entry or knowingly or intentionally refuses to leave the real property of another person, having been asked to leave by the other person or that person's agent commits criminal trespass, a Class A misdemeanor.