U.S. Code § 2332a is domestic criminal law. If Saddam Hussein blew up something that wasn’t American the US wouldn’t have jurisdiction and it wouldn’t apply. If as an act of open warfare Hussein ordered grenades thrown at American soldiers it wouldn’t apply as that would indeed have been a lawful act by a foreign head of state. If Hussein ordered the bombing of a nightclub that targeted and killed a bunch of off-duty American soldiers it might apply on the basis that the act was unlawful terrorism. If Hussein ordered a sarin attack on a bunch of Americans that would not be lawful as it would violate both the Geneva Protocols, which Iraq acceded to in 1931, and traditional international law.
And remember, WMD in domestic criminal law =/= WMD in international diplomacy.
