What Makes Chemical Weapons 'Red Line' in Syria? The ghastly images reveal rows of the dead, many of them children, wrapped in white burial shrouds, and survivors gasping for air, their bodies twitching, foam oozing from mouths. This was unlike any other scene in Syria's brutal civil war, where bombs and bullets have killed and maimed tens of thousands over the past 2½ years. The Aug. 21 attack on the rebel-held suburbs of Damascus was carried out, the U.S. says, with chemical weapons. It crossed what President Barack Obama calls a "red line" and, he says, demands a military response against the government of Syrian President Bashar Assad. But in a war where only a fraction of more than 100,000 Syrian deaths have come from poison gas - the Obama administration says more than 1,400 died in the attack - what is it about chemical weapons that set them apart in policy and perception? Some experts say chemical weapons belong in a special category. They point to the moral and legal taboos that date to World War I, when the gassing of thousands of soldiers led to a worldwide treaty banning the use of these weapons. The experts also say these chemicals are not just repugnant but pose national security risks. "The use of nerve gas or other types of deadly chemical agents clearly violates the widely and long-established norms of the international community," said Daryl Kimball, executive director of the Arms Control Association, a nonpartisan research group in Washington. "Each time these rules are broken and there's an inadequate response, the risk that some of the world's most dangerous weapons will be used in even further atrocities is going to increase - that's why here and why now," he added. Others contend there is no distinction and that the U.S. should focus on protecting Syrian civilians, not on preventing the use of a particular type of weapon against them. "The Syrian regime commits war crimes and crimes against humanity every day," said Rami Abdel-Rahman of the Syrian Observatory for Human Rights. A war crime is a war crime. The Britain-based anti-regime monitor of the fighting says it has been compiling a list of the names of the dead from the Aug. 21 attack and that its toll has reached 502. The exact number of those killed is not known. The Obama administration reported 1,429 people died, including 426 children, citing intelligence reports. Others have provided lower numbers. The Assad government blames rebels. They came a year after Obama said the use of such lethal weapons in Syria would carry "enormous consequences." "A red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized," Obama said. Last week, Obama shifted the onus. "I didn't set a red line," he said. "The world set a red line" with a treaty banning the use of chemical weapons. The president's call for a punitive strike has met with strong resistance and skepticism, both on Capitol Hill, where he's seeking congressional approval, and in a nation weary of a decade of war in Afghanistan and Iraq. At last week's Group of 20 economic summit in St. Petersburg, Russia, Obama said he put the issue before Congress "because I could not honestly claim that the threat posed by Assad's use of chemical weapons on innocent civilians and women and children posed an imminent, direct threat to the United States."