There is nothing novel about the legal basis presented by Amb. Powers, let alone anything extraordinary about it.
The quality of his analysis is demonstrated by his parenthetical 'does anyone remember how World War One got started?' I certainly do, and it had nothing whatever to do with military action being taken across a nominal border against a body of rebels who could not be controlled by the nominal sovereign of the territory they held, after the rebel group had invaded another country. It began with the assassination of a prominent royal of one country, contrived by the 'special service' of another country, which appealed to a powerful protector to try and ward off the hostile reaction it had courted. When the protector agreed to threaten the aggrieved party, a series of interlocking alliance obligations was triggered, along with the need to be in a position of readiness with military structures which took a good deal of time to get assembled and in position. Governments began to mobilize because they knew others were mobilizing, or would do so very soon, and that immediate invasion would commence once they had. The dissimilarities are obvious, as is the slack and lazy thinking, or the bleak ignorance, required to present them as jibing.
Mr. Parry may once have been a good journalist, but he is an extremely poor op-ed columnist....