He's talking about weapons that were used against the Kurds in 1988. These would be chemical weapons which we sold to Iraq and, by 2002 when the Iraq WMD drumbeat kicked into high gear, those chemical weapons would've been long since expired and useless.
Santorum once thought he found WMD in Iraq. But those chemicals were also expired and useless -- much like Santorum's re-election campaign. I'm seriously thinking that Huckabee is Santorum with zingers.