Killing prisoners of war is a violation of the Geneva Conventions. Once soldiers clearly indicate an intention to surrender, they cannot be attacked and must be safely taken into custody. The Ukrainian government has repeatedly pointed at Russian troops killing unarmed and surrendering soldiers as proof of Moscow’s lawlessness.

Russia has stated foreign fighters (i.e. Russians fighting for Ukraine) are unlawful combatants entitled to no protection under the Geneva Conventions, captured foreign fighters will not be given prisoner of war status, and captured foreign fighters will be prosecuted as mercenaries.

While maybe morally detestable, it seems only legally questionable by Russians own logic.