Sorry, but i highly doubt that any policemen would enable such a lock on their gun as they would not ever be able to use their gun in the instance where they have gloves on their hands....
Fingerprint locks are not acceptable to me because of this. On the other hand, the already existing 'Magna-Trigger' and 'Maglock'(for 1911's) are semi-widely deployed. They're keyed to universal magnetic rings though, not anything serialized, making them the equivalent of bathroom dispenser locks - they won't stop or slow down anybody that came prepared to defeat them.
RFID is an option, but that would be more vulnerable to EMP*/interference. Also, the one RFID gun I remember has a 20" unlock range with the watch, which would mean that the gun would still fire in the majority of 'just disarmed the officer' cases I've read, many of which had the officer struggling with the perp for the gun when he was shot, which means that the wristwatch would be within 20" when the trigger is pulled.
Really, I think what the legislation is trying to do is make the guns more expensive in the hopes that only rich(safe) people would buy them, same idea with anti-Saturday night special laws back in the '70s. Back then they recognized that criminals overwhelmingly carried cheap small handguns, not expensive and bulky 'assault weapons', so they tried to ban 'cheap'. A 1911 was in no danger, but a .280 was.
*Honestly, I don't think this is that good of an excuse. Good EMP is actually hard to do.