This sounds like an ultimatum—like war talk. OK what if he demands we remove all of our nukes? or if Putin demanded we dismantle our own poison gas? Kerry looks like he’s investing in war. maybe this will all blow over but I fear its going to blow up in our faces. Odds are maybe 20% to 80% it will end with WW III or a limited naval war (30%- 70%) Will NATO support us if Russian ships blow ours out of the water to defend Syria? Will we blow Russian ships out of the water at any threat? Scary times indeed. And we have a fool in the Oval Office.
We will be the aggresor, so the NATO treaty will not apply.
All you say is true except such considerations are beyond the capacity of Kerry answering the question of what can Assad do.
He is not quick enough on his feet to make those calculations.