After refusing to buy the U.S. evidence that the Syrian government was responsible for chemcial weapons attacks on its own people, Russia now says that there was a chemical attack in that country, but it was the rebels who were the responsible party. Back in April, U.S. officials formally accused Bashar al-Assad's forces of using chemical weapons and took their case to the United Nations, the Europeans, and the Russians in the hope of spurring international action. Moscow dismissed the claims as "unconvincing," but now they have submitted their own scientific analysis of a projectile that was fired on the city of Aleppo and agreed with claims that the weapon was filled with sarin gas. They just don't agree on the source.
The basis of their claim that it was rebel fighters appears to be that the weapon they found was not a standard munition like the kind that would be manufactured for a legitimate army. Therefore, it must have been rigged up by the lesser-equipped opposition. It's not clear how such primitive fighters would have got their hands on sarin gas without the weapons to deliver them.
It's also not clear what Russia expects the United Nations to do with this information. For two years now, Moscow has been doing everything possible to prevent foreign intervention in Syria, arguing that it's not right to interfere in another country's affairs. And it's been two months since the U.S. leveled the same charge against the Assad regime and nothing has come of it. (In part, because the evidence is not airtight, but that's another story.) The war continues and despite talk on all sides that chemical weapon use is totally unacceptable, the evidence that someone is using chemical weapons is too strong to ignore. Yet, somehow it probably will be.