As you note, police are not subject to the laws of war -- they routinely use devices (pepper spray, tear gas, hollow-point bullets) that would be war crimes were they to be used in an armed conflict.

This is not problematic on the face of it -- police are expected to use non-lethal tactics whenever possible, and the laws of war are hugely biased towards killing rather injuring because overwhelming your opponent with casualties is considered inhumane in war.