The law of war is based on two fundamental principles: first, the distinction between the targeting of combatants and civilians; second, the requirement of proportionality in attacking targets that include both. –Under these principles, Israel’s actions were completely justified.
The individuals who were given beepers, radios and other communication devices by Hezbollah were clearly combatants. Their deaths and injuries were lawful, even if they were shopping or walking when blown up.
There is no magic formula. The military action must simply be reasonable under the circumstances. Hezbollah, a non-state actor declared war on Israel.