The federal gov't already requires that all handguns sold by FFLs be delivered with a locking device:
18 U.S.C.A. § 922 (West)
(z) Secure gun storage or safety device.--(1) In general.--Except as provided under paragraph (2), it shall be unlawful for any licensed importer, licensed manufacturer, or licensed dealer to sell, deliver, or transfer any handgun to any person other than any person licensed under this chapter, unless the transferee is provided with a secure gun storage or safety device (as defined in section 921(a)(34)) for that handgun.
Negligence law already provides a remedy for negligent entrustment, whether it be negligent entrustment of a firearm, automobile, etc.
Besides, what's to make me believe that the requirement suggested by the OP would have any more effect on the non-law-abiding than any other law would?
Originally Posted by rebs
Its just a thought, I have no idea how to prove you have a gun safe or locks other than a receipt for payment.
Oh, that's easy. Let's just have every law-abiding gun owner sign a Fourth Amendment Waiver so that the gov't can come do in-house safe inspections on demand. [/sarcasm]