Peeping Tom laws—also known as voyeurism laws or invasion of privacy laws—generally make it illegal and a criminal offense to peek into windows or doors on private property to view a person who is fully or partially naked for the purpose of sexual desire or gratification.

Peeping Tom laws vary from state to state and some states require that the victim not realize he or she was being viewed and that the victim had a reasonable expectation of privacy (was in a place where it was reasonable to expect privacy). And some states specifically address the use of unmanned aircraft (drones), cameras, video cameras, and binoculars in connection with such peeping. Some state statutes specifically prohibit peeking into bathrooms, dressing rooms, showers, and baths. And some states characterize this criminal offense as trespassing with the intent to peer or peep.

Peeping Tom laws are located in a state’s statutes—often in the penal or criminal code.

In Montana, Peeping Tom laws are addressed under the state's privacy and voyeurism statutes. Montana Code Annotated § 45-5-223 specifically criminalizes surreptitious visual observation or recordation, making it illegal to watch or record a person without their knowledge in situations where they have a reasonable expectation of privacy, such as in a bathroom, bedroom, or dressing room. This includes any place where a person may be expected to disrobe. The law covers the use of devices like cameras and video equipment. It is a crime to observe or record a person for the purpose of sexual gratification without their consent, and this applies to both private and public places where an individual would have a reasonable expectation of privacy. The use of drones for such activities would also fall under these prohibitions. Additionally, Montana law may consider such acts as criminal trespass if done with the intent to observe or record someone in a private setting. Violation of these laws can result in serious criminal charges, including felony charges depending on the circumstances of the offense.