California, much like many other states, has laws that prohibit the use of phones while you are driving. As useful as they are, phones can be incredibly distracting. Even looking down for a few seconds to change a song, read a message, or take a photo can be more than enough time for something bad to happen on the road.
In California, it is illegal for any driver to have a phone in their hand while they are driving. Having a phone in your hand means there is one less hand on the steering wheel. Having a phone in your hand can also tempt you to check it. Another law prevents drivers under the age of 18 from using a phone, even if it is in a hands-free position. That being said, these general laws only apply to the person who is behind the wheel. All passengers in the car are free to use their phone as they please, as long as it does not distract the driver.

Hands-Free Use
There are some general cases where the average driver is allowed to use their phone like in a hands-free position. A phone mounted in a holder is fine if it is simply being used for navigation purposes or to change between songs. Using your phone for map navigation only requires you to glance over every now and then for updates and it does not require you to even touch it.

Exceptions
Although California has laws in place that prevent drivers from using their phones while they are behind the wheel, there are some exceptions to the rules. The biggest and most obvious situation is when there is an emergency of some sort. If you need to contact the fire department, a hospital, the authorities, or any other party, regarding an emergency situation, you are free to contact them immediately. These sorts of situations require quick responses.