In the United States it is illegal to use any equipment to purposefully interfere with cellphone communications, according to the Federal Communications Commission. This law extends to anyone who manufactures, sells or uses a device to disrupt cellphone signals, GPS device operation, police radar equipment or wireless Internet signals.
The Communications Act of 1934 makes it illegal to willfully interfere with radio communications, which includes cellphone signals, reports the FCC. The act also forbids the manufacturing, importing, marketing and sale of devices that cause radio interference and sets consequences for not following the law. These consequences include the seizure of unlawful equipment. Blocking signals presents a safety hazard by potentially disrupting emergency calls and communication between emergency response personnel.
The FCC's rules expand upon the act with section 2.803, which further prohibits the sale and use of these devices, and section 2.807, which allows for some exceptions by the U.S. government. The criminal code, which is enforced by the Department of Justice, sets specific penalties for disrupting cellphone signals, including fines and prison sentences. These laws do not require malicious intent, making devices designed to create quiet zones in restaurants as illegal as those used by people with criminal intent, according to the FCC.