It is in the world's interest that chemical weapons not be used with frequency. Ultimately what I am more concerned about is America's reputation and ability to force other countries to compliance via said reputation. I can see value in America drawing the line and saying 'cross it and you fucked.' That was a major problem I had with Obama's actions in Syria. They were tepid and when lines were crossed he didn't effectively deter Syria's defiance.
Either America says "We don't like chemical weapons but not our business" or "We don't tolerate chemical weapons." One could argue what is the appropriate response A or B. However no one can justify declaring B and then not enforcing it.