Apparently their national law "nobody may own a firearm or firearms, or a sword or swords" isn't strong enough. Apparently the authority of the police to confiscate legally owned firearms, without a warrant and without cause, and not even give them back even if they did so in an illegal manner, isn't strong enough.

Apparently Japan needs to make it a death penalty offense for anyone to be found in possession of a gun.
"the fundamental principle that a government and its agents are under no general duty to provide public services, such as police protection, to any particular individual citizen." Warren vs. The District of Columbia.