In 2016, California passed a law which included Proposition 63, which among various gun safety reforms included a ban on the possession of large capacity magazines, which took effect on July 1, 2017. This law required individuals who owned large-capacity magazines to permanently modify them so that the magazine would not accept more than 10 rounds. And banned the sale, manufacture, and transfers of magazines containing more than 10 rounds

At this time, magazines that can hold more than 10 rounds is illegal in the state of California, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey, New York and the District of Columbia

Yes, pistol magazines do have to follow the magazine capacity limit.