Syrian Clarification, S'il Vous Plait

Since I'm on vacation and mostly away from Internet or TV access, I'm very much behind on the news. Hopefully you guys have been paying more attention than me, so maybe you can explain: what's this I hear about allegations that Syria's government is using nerve gas on the rebels? I could've sworn that a few months ago, they claimed it was the rebels using nerve gas against the government. Is the US about to start yet another useless war on false pretenses? We've got so many going now, I can't even keep track of them all.