Having said that, if chemical weapons were used, by the Assad dictatorship, I would favor a missile strike against all known chemical weapons depots. I would also support a total arms embargo against the Assad dictatorship in such circumstances.
If, however, the chemical weapons were used by the anti-Assad forces, I would favor the U.S. working within the Security Council and in collaboration with the world's major powers to secure a total arms embargo on the anti-Assad forces. The latter would be difficult to achieve, as neighboring states supporting those elements could "cheat," because such an embargo would ultimately doom those forces to defeat.
Neither side has shown any meaningful regard for civilian protections. Neither would deserve sympathy if punishment for their use of chemical weapons leads to their loss of such weapons (missile strikes were the Assad dictatorship responsible) or battlefield defeat (if the anti-Assad forces were responsible).
I still believe that had a total arms embargo been imposed on both sides to the sectarian conflict, the environment would have been more conducive to diplomacy, as calculations for a military breakthrough would have been much less favorable during the stalemate that had existed until fairly recently. But that was not undertaken and the result has been more conflict and more conflict-related casualties.