What are some of the laws that regulate listening to phone calls on a scanner?

A federal law commonly known as the Counterfeit Access Device Law makes it illegal to use a scanner to eavesdrop on wire or electronic communication knowingly and with the intent to defraud, reports Privacy Rights Clearinghouse. According to the law firm Wallin and Klarich, California has a similar law.

Wallin and Klarich report that under California Penal Code Section 632, it is a crime to use any device to listen in on someone’s conversation without their consent. However, merely stumbling onto a conversation with a scanner is not illegal under this law as long as a person does not intentionally manipulate a device in order to eavesdrop and does not record the conversation.