Keep in mind that strategic level bombing carried out during World War I and World War II was permissible under the Hague Conventions of 1899 and 1907, and no modern restrictions were placed until the Geneva Convention of 1949. Under the Hague Conventions the definition of a "defended settlement" included the presence of any military units or anti-aircraft weapons, and any defended settlement was a legal target. Even in the Geneva Convention of 1949, the definition of "lawful combatants" includes civilian inhabitants who spontaneously take up arms to resist invaders, so any civilians who fight back with weapons can also be treated equally to other soldiers.
Also keep in mind that not all countries are necessarily bound by international military laws. The United States has not ratified Geneva Convention Protocols 1 and 2, so if the US does not have any national military restrictions of its own, then US military forces are not legally prohibited to:
[ul]- endanger prisoners or subject them to unnecessary or nonstandard medical procedures (Protocol 1.11.1)
- perform physical mutilations, medical or scientific experiments on prisoners (P 1.11.2)
- remove tissue or organs from prisoners for transplantation (P 1.11.3)
- attack medical units (P 1.12)
- withhold information about missing or dead people (P 1.33)
- offer and give no quarter, that is, ignore surrender (P 1.40)
- attack people parachuting from aircraft in distress (P 1.42)
etc.[/ul]
Some unpleasant realizations for people carrying weapons around - if you start using your weapon, you become a "lawful combatant" rather than a "civilian".