and to go further since there did seem to be a goodly amount of consequences to the ignored red line. Much of this seems to be more about proof than anything else:

"Western powers opted for the path of diplomacy instead. Assad’s government was forced to join the international Organisation for the Prohibition of Chemical Weapons (OPCW) and a US-Russian agreement to dismantle Syria’s chemical weapons capability was signed in Geneva on September 14, 2013.

In August 2014, the White House hailed the destruction of 581 tons of sarin and 19.8 tons of mustard gas under the OPCW’s supervision.

Nevertheless, in August 2016, a UN and OPCW commission known as the Joint Investigative Mechanism (JIM) claimed that Syrian military helicopters had dropped chlorine on at least two places in northwestern Idlib province – in Talmenes in 2014 and Sarmine in 2015. Then in October 2016, another JIM report concluded that the Syrian military had carried out a chemical weapon attack, likely using chlorine, in Qmenas, also in Idlib, in March 2015.

But it was not until the April 4 attack on Khan Cheikhoun that the West decided to take military action. At least 83 people died in the air raid on rebel-controlled territory in Idlib province, their symptoms suggesting they were victims of a chemical attack."