Imagine your car gets stolen but your cell phone is in it. The police can ask the phone company to turn on a service that tracks your phone's location, and help the cops find the thief.
"Law enforcement can ping users' cell phones and other devices and learn where they are in real time," says Chris Hoofnagle, director of the Berkeley Center for Law and Technology.
Hoofnagle says police around the country "ping" cell phones every day, to catch suspects in the act. But for phone companies, it's a thorny issue. They get so many police requests, Hoofnagle says, they need full-time staff to handle them.
"Most companies do not want to provide this information to law enforcement, but they feel pressure to do so," says Hoofnagle.
The companies don't want it getting out that they'll let police "ping" your phone if it's involved in a crime. Because, well, lots of customers are already freaked out over digital privacy. And while tracking your phone could help solve a crime in the moment, it could also violate rights, without proper cause.
Several states are wrangling with the issue. New Jersey went the opposite direction of California. Police there must get a warrant to track a cell phone.