Two questions are raised by reports of this attack. The first, of course, is whether or not it happened the way Syrian rebels said it happened. That is why immediately dispatching the UN team, already in-country, to the affected areas is so vital. If this process worked the way it should, they would be there already. If the Syrian regime denies the UN inspectors permission to visit these areas, well, that is kind of an answer in itself.
The second question is, why would the Assad regime launch its biggest chemical attack on rebels and civilians precisely at the moment when a UN inspection team was parked in Damascus? The answer to that question is easy: Because Assad believes that no one – not the UN, not President Obama, not other Western powers, not the Arab League – will do a damn thing to stop him.