Jamming a cell phone is illegal in the U.S. Very illegal. And not just by ordinary citizens. It's illegal for theater and restaurant owners to jam calls, and even state and local police or prison officials. The U.S., in fact, has the strictest laws in the world against jamming cell calls.

U.S. law prohibits not only buying, selling, carrying or owning a portable mobile phone jammer, but also posting a Craigslist ad that claims you're selling one. If you're caught with a jammer, you could face up to $11,000 in fines and up to one year in prison.

The ban against mobile phone signal jammers isn't new. In fact, it's the musty old 1934 Communications Act that bans the jamming of any commercial radio communication, a law that predates not only jammers but cell phones themselves.

Mobile phone jammer laws vary throughout the world. In the U.K. and Japan, for example, anyone can own a jammer -- as long as they don't use it.