This link is to the Organization for the Prohibition of Chemical Weapons website. The link specifically takes you to information regarding the Chemical WEapons Convention where you can see the states that have signed it, the goal of the convention, and the specific agreements that a state must agree too.
Syria officially joined the United Nations convention banning chemical weapons, the Organisation for the Prohibition of Chemical Weapons (OPCW). The treaty requires all countries that join it to eliminate their chemical weapons, including stocks and related facilities. Syria is the 190th country to join the OPCW.
UNODA- United Nations Office for Disarmament Affairs. This site discusses the use of the Geneva Protocol in regards to chemical weaponry. The protocol prohibits use of chemical weaponry in warfare but does not prohibit stock piling. Geneva adopted the chemical weapons convention which established the organization for the prohibition of chemical weapons (OPCW)
Rule 74 prohibits the use of chemical weapons. Only 13 states are not part of this party but at least 3 consider the use of chemical weapons unlawful. This link provides different groups that prohibit the use of chemical weapons in both non international and international armed conflicts.
This article states that if Bashar al Assad's use of chemical weapons in a suburb is true then why isn't the United States acting to protect the Syrian civilians. This article, contrary to the one I posted earlier, says that Syria is legally at fault in regards to chemical warfare because they signed the Geneva Convention.
An estimated 100,000 people have died in the Syrian civil war including women, children, and other innocent bystanders. Chemical weaponry creates a different psychological aspect of immense fear that other weapons do not. It's terrifying because you can't see it or smell before it hits you. The weapons kill in minutes and are indiscriminate.
Why is there particular revulsion over such attacks versus conventional warfare? The population feels they can do nothing to protect themselves. Chemical weapons are invisible and indiscriminate killers than could affect anyone at any time. The fear can even cause symptoms that aren't real.
The article looks into why it is not illegal for Syria to use chemical warfare against its people. It covers several international treaties including the Geneva Convention and explains why Syria is not legally at fault for the treatment of their civilians.