In California, it is illegal for an adult (someone 18 or older) to have sex with a minor (someone younger than 18), even if the sex is consensual. Those who break the law have committed statutory rape.

Is it OK for someone over 18 to date a minor?

California – The age of consent in California is 18. It is illegal for anyone to engage in sexual intercourse with a minor (someone under the age of 18), unless they are that persons spouse. California employs a tiered system where the greater the difference in age, the greater the penalty.