I read with interest about US Patent application 20060117632, which proposes to apply the notion of cryptographic accessory control to individual bullets in firearms. Only after an authentication protocol has convinced the tiny microprocessor in a cartridge that it is OK to potentially kill someone, it will close a transistor switch that normally blocks the electrical ignition mechanism.
It does not seem to me technically infeasible, or even cost prohibitive, to apply security mechanisms comparable to those we have come to expect to be used in weapons of mass destruction also to smaller weapon systems that were designed to kill only a few people at a time.
(The idea could be extended. If we add a chip to each cartridge, we might as well place it into the bullet itself. The bullet processor could then store in its NVRAM an audit log of the certification chain that ultimately authorized the firing of this bullet. With the right packaging, NVRAM chips can be made extremely tough and withstand hundreds of km/s² acceleration, much more than the conditions a normal bullet faces when penetrating a body. Having a log file in each bullet that identifies who is responsible for firing it could make the forensic investigation of shootings and war crimes so much easier.)