How can we reform the Law of War to allow heads of state and government buildings to be targeted?

It doesn’t make any sense to me that leaders of countries can declare war with total immunity from its violence, unless they’re actually fighting themselves, which in most cases they are not.

They have nothing to lose when they declare war, so why should they be allowed to put all of us at risk?

How can the Laws of War be changed to hold politicians accountable for their actions and make them think long and hard before engaging in wars? Maybe alternatively, all politicians including the president/PM/leader should have to serve in the military as well.