Why must jus in bello apply equally to all parties?

War in the classical sense: a state of armed hostilities between states, recognized and governed by the laws of war — a legal status (with its consequences: treaties, neutrality, enemy- property rules) as much as a fact. The modern era's reform: the UN Charter's outlawry dissolved war's legality — modern doctrine prefers "armed conflict" (the Geneva Conventions' term): any armed confrontation between states (international) or between a state and organized armed groups (non-international), whatever the declaration. Types: declared/undeclared war; total/ limited; international vs. non-international armed conflict (Common Articles 2 and 3's divide); conventional/guerrilla/cyber-enabled; the "hybrid" spectrum below the armed-conflict threshold.