It seems pretty clear that George W. Bush and Dick Cheney, behind their front man Colin Powell, have destroyed the moral authority of the United States by invading Iraq under false pretenses and fake intelligence. Obama now pays the price because he has to rely on the same discredited intelligence agencies, who bowed to political pressure and issued intelligence analyses requested by the White House, rather than supported by facts.
Because we have no moral authority, Obama is wasting his time trying to marshal intelligence to support his invasion of Syria. It's not clear what he will do, but it certainly appears that it will be a military strike of some kind that would constitute an act of war. Syria seems unlikely to respond militarily, but would have a legal right to do so under international law. Syria may have committed unspeakable offenses against its own people, but it has not attacked the United States. And there is no provision under the Chemical Weapons Convention which makes the US the unilateral enforcer of the Convention.
Under the circumstances, Obama should just go ahead and do whatever he and his advisers think is appropriate "punishment" for Syria, without worrying about whether Syria really should be punished and if so, how. Act and get it over with!