Principle: Any person or business knowingly aiding someone' s infringement on a copyright is also guilty of copyright infringement. Application: Grandview Department Store, which features a self-service photo-printing kiosk, is guilty of copyright infringement since a customer using the kiosk infringed on a wedding photographer' s copyright by printing photographs whose copyright is held by the photographer.
The assumption that owners of self-service facilities should monitor those facilities in order to ensure that they are not used for illegal or unethical purposes most helps to justify the application of the principle.