In response to the threats of ambush marketing and other forms of trademark infringement, organizers of major sporting events have sometimes required host countries or cities to implement special laws that, going beyond standard trademark law, provide regulations and penalties for advertisers who disseminate marketing materials that create unauthorized associations with an event by making references to specific words, concepts, and symbols. Organizers may also require a city to set up "clean zones" in and around venues, in which advertising and commerce is restricted to those that are authorized by the event's organizer—specifically, the event's official sponsors.