I'm confused as to what constitutional law you feel was broken... truly I am.
We are in Iraq, there in wartime by congressional authority and by the permission of the Iraqi government, moreover, we have the legal right to self defense. The present military operations was ordered under a previous president - president Obama - and our operations today is a continuation of the same. Iranian backed militias attacked U.S. troops lawfully present in a combat zone under valid legal authorities. America's military response isn't limited to immediate self defense, we can also act to remove an active threat. That threat includes enemy commanders.
The true act of war was thus Iran's by putting one of its commanders, boots on the ground, in Iraq to assist in planning and directing attacks on U.S. forces. America is entitled to respond to that threat.
So my question to you is this - where in the constitution does it say our president didn't have this authority?
Your the one challenging this, so where is your proof that the president of the United States doesnt have the right to defend U.S. troops and our embassy (an embassy is sovereign U.S. soil) in a time of war by killing commanders plotting further attacks against us?