Which would be everything but sticks and knives. Heck, even drowning someone would be using H2O as a 'chemical weapon'.
WP is not a "chemical weapon". It is a horrifyingly effective anti-personnel weapon that should be used more against the muslims than we are using it now. In fact, I propose that the US military bring back napalm and flamethrowers. The latter especially were very effective in the Pacific Campaign in WWII against Japanese soldiers who were holed up in caves, spider holes, and bunkers. Besides being effective, they adversely effect enemy morale and instill fear. Time to take off the gloves, IMHO.
IED's are chemical weapons also, then. So is everything else besides kinetic energy weapons.
Second - Al Queda never signed any pact or treaty regarding human rights. They don't represent a recognized country and they aren't following the Geneva Conventions. They target noncombatants, don't wear uniforms, etc.