India, Oct. 22 -- In March this year, the Donald Trump administration announced that American policy didn't prohibit the "development or employment" of lethal autonomous weapon systems (LAWS). A few months later, it admitted to positioning weapons in space. Both instances set precedents for other countries and raise several questions about what is acceptable in a war.

Every technological revolution in warfare has tested the rules, customs, and moral restraints that seek to limit its consequences. For centuries, war was governed by conventions grounded in the understanding that even conflict must have limits. These reflected fundamental distinctions between combatant and civilian, military necessity and unnecessary suffering, and what cou...