The United States, Russia, France, Israel - suddenly everyone is concerned. Weapons of mass destruction, they shout from the sidelines, something must be done. Regional security is at stake. If Syria's weapons continue to pose a threat, outside powers say they will militarily intervene.
Have we been here before? A decade ago, the international community was worried about Iraq's weapons of mass destruction. They were not concerned that Saddam Hussein had been brutalising his people, or that international sanctions had destroyed whole communities, or that Iraqis - as a direct consequence of sanctions - were living without food and medicine. None of that mattered; only the weapons. Which turned out not to exist.
The obsession with chemical weapons has resurfaced in Syria. These weapons do exist - the Assad regime admitted as much when it said it would not use its stockpile against civilians, but threatened a chemical-weapon retaliation in the case of foreign intervention.
Any major intervention should be considered as carefully now as it was before. For 17 months the opposition has fought against the Baathist regime, and for 17 months the outside world has dithered. The United States said this week that the use of chemical weapons would be "unacceptable". Was it acceptable for the Syrian regime to slaughter its own people? Was it acceptable to rain mortar shells into residential areas, for regime thugs, the shabbiha, to kill women and children? The regime has done all this while the world watches.
No one will question that chemical weapons pose a fearsome threat. The former Iraqi regime's attacks on Iran during the 1980s war, and attacks against its own people, still conjure horrifying images of suffering. Israel's use of white phosphorous (banned by international law and arguably constituting chemical weapons) in the 2008 Gaza War also exacted a terrible civilian toll.
The threat of such weapons falling into the hands of Al Qaeda-related groups, which may have joined the Syrian opposition, is frightening; it's bad enough that the Assads have them.
While there is a potential threat, Syrians face many present dangers every day. The use of chemical weapons would be shocking but - worse from the perspective of the crumbling Assad regime - it would be a war crime and would demand foreign intervention.
Of course, the Assad regime is already guilty of atrocities. Syrian lives, regional security and Middle East stability are all at risk in this conflict. Chemical weapons grab attention - and headlines - but Syrians know well that conventional weapons kill just as well.