Though Syria gave up its actual chemical weapons arsenal in mid-2014, a UN report has blamed the Syrian military for two incidents after that period involving the release of a “toxic substance” which had effects similar to chlorine gas.
The two incidents, in April 2014 and March 2015, involved Syrian helicopters dropping an unspecified device and then the release of the “toxic substance.” It is unclear whether this meant the devices contained the substance, or simply caused toxic leaks in those residential areas.
The same report also confirmed an August 2015 incident in which mustard gas was released in the town of Marea, an incident which was blamed on ISIS, as the only force in the area with the capability to use sulphur mustard-based weaponry.
None of these are really advanced “chemical weapons” in the modern sense, though the ISIS incident demonstrates some rudimentary development to that end. Though hawks are likely to present the incidents involving the Syrian military as “violations,” in practice the primitive and unspecific nature of what happens underscores that Syria’s actual chemical weapons, among the most advanced and substantial extent arsenals as of the early 2010s, was no longer in play.
The US ambassador to the UN, Samantha Power, has already urged the security council to take “strong and swift action” against the perpetrators, particular the Syrian government on the thinnest of evidence.
From an Associated Press report:
“‘The information suggests the involvement of both the government of the Syrian Arab Republic and other actions in these alleged incidents,’ the team’s report said.”
The ‘alleged’ implies that the UN-OPCW is even sure the event occurred (probability <0.5) and the 'suggest' implies that the UN-OPCW has no real evidence for what occurred(probability <0.5). So the probability that the headline is true is less than 0.25. You wouldn't even get a look-in in an English civil court with evidence that weak, let alone a criminal court.