S: http://www.ohchr.org/EN/ProfessionalInterest/Pages/UseOfForceAndFirearms.aspx (last access: 29 July 2015); http://www.cbp.gov/sites/default/files/documents/UseofForcePolicyHandbook.pdf (last access: 2 September 2014).
N: Public international law governs the relations between States themselves, or with and between international organizations. It helps maintain a viable international society. As far as armed conflict is concerned, a distinction is made between jus ad bellum or the law that outlaws war – essentially the UN Charter that prohibits the use of force in the relations between States, except in cases of self defence or collective security – and jus in bello or the law applicable in time of armed conflict.
The latter does not make any judgement on the motives for resorting to force.
S: https://www.icrc.org/eng/assets/files/other/icrc_002_0943.pdf (last access: 29 July 2015)