Those who raise the issue of WMDs in Iraq (or the incubator babies of the first Gulf War, or the second Tonkin Gulf incident) need to have another look at the images. This is primae facie evidence. There was never WMDs in Iraq. There were no incubator babies in Kuwait. But it should be abundantly clear, from the images and the medical reports, that civilians have been killed from poison gas attacks.
The balances of probabilities is that this was conducted by regime forces, a government that has one of the world's highest stockpiles of chemical weapons but refuses to sign the treaties limiting their use. The government has also showed a cavalier disregard for the indiscriminate use of heavy weapons against civilian non-combatants. It seems implausible that any of the rebel factions (and some of them are at least as bad as the Assad regime) have the capacity to use or deliver such a quantity of poison gas. The motive is also unlikely; shelling a region that you currently hold.
Attentive reviews of this atrocity will be quick to point out that the Syrian government shelled the location again after the chemical weapons attack, which will make any UN investigation for evidence of delivery more difficult. They will also point out that China and Russia, once again, blocked a Security Council resolution for access to the site immediately after the event.
http://www.abc.net.au/news/2013-08-27/syria-chemical-weapons-attack-dama...