From an FCC Enforcement Advisory, 2011…
Why are jammers prohibited? Use of jamming devices can place you or other people in danger. For instance, jammers can prevent 9–1-1 and other emergency phone calls from getting through or interfere with law enforcement communications (ambulance, fire, police, etc). In order to protect the public and ensure access to emergency and other communications services, without interference, the FCC strictly prohibits the use, marketing, manufacture, and sale of jammers.