Assad has already agreed to give up Syria's chemical weapons stockpile, and the US and Russia, alongside the EU, all attest to this being a real move on Syria's part to be a willing and trustworthy partner in the end of this horrible and vicious civil war. Assad should be allowed to pursue this.
Assad wasn't supposed to have chemical weapons in the first place. He is clearly a dangerous megalomaniac with no regard for human life. Even if weapons inspectors try to destroy his stockpiles, he will certainly retain some, or he will produce more. The only solution is to remove Assad from power.