Certainly, it’s called the Law of Armed Conflict (LOAC) or International Humanitarian Law (IHL). The Red Cross provides good explanations [here](https://www.icrc.org/en/war-and-law%E2%80%83).
Most important principles in IHL:
1. Principle of distinction: military objectives may be specifically targeted, civilian objectives not. Those working as medics, the wounded and those who have surrendered may not be targeted.
2. Principle of proportionality: any attack is going to lead to casualties. A state should only attack if the anticipated military advantage outweighs the risks of civilian casualties, as judged before the attack happens.
3. Principle of precaution: a state should do everything it reasonably can to reduce the impact of hostilities on civilians. Certain weapons are therefore not allowed, since these likely cause unneccessary suffering.
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