The Californian law comes after the state of Washington passed a similar law covering radio frequency identification (RFID) technology earlier this year.
US citizens increasingly use RFID to gain access to offices, properties, children's nurseries, parking lots and others areas.
The possibility of hackers wirelessly "skimming" people's RFID smartcards has also been given wide publicity in the UK. New passports are already equipped with RFID chips and similar devices are integrated into London Transport's Oyster travel cards.
Dutch researchers have already been to London to hack into the Oyster system. They managed to launch a "denial of service attack" on a ticket gate.