Does Obama Have to Act in Syria?

President Obama has warned Syria that using—or even transporting--chemical weapons would be a “game changer.” Britain, France and Israel now claim that the al-Assad regime has thrown down the gauntlet. Syria denies the charge, but is the evidence credible? Will the US have to respond? What are the available options?

Banner Photo © Reuters - Handout photo from SANA, Syria's national news agency.