To be fair to the States and Trump, what is the point of international law and limits if countries can just ignore them? The Russsians have vetoed several attempts through the UN for other action in Syria including financial.
However, you would have like to have seen Tillerson try to get some co-operation with the Russians about doing an investigation when he meets them next week first before such strikes.
Should make the meeting next week interesting, unless thats cancelled.
