"“(A) any destructive device as defined in section 921 of this title (i.e. explosive device);"
and section 921 has :
"(4) The term “destructive device” means—
(A) any explosive, incendiary, or poison gas—
(i) bomb,
(ii) grenade,
(iii) rocket having a propellant charge of more than four ounces,
(iv) missile having an explosive or incendiary charge of more than one-quarter ounce,
(v) mine, or
(vi) device similar to any of the devices described in the preceding clauses;
(B) any type of weapon (other than a shotgun or a shotgun shell which the Attorney General finds is generally recognized as particularly suitable for sporting purposes) by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, and which has any barrel with a bore of more than one-half inch in diameter; and "
You're conflating the military definition of WMD (which has essentially always been related to CBRN) with the U.S. civilian legal definition of WMD, which pre-dates the invasion of Iraq.
according to current definition of WMD, Saddam had(and a billion other people have):
http://www.fbi.gov/about-us/investigate/terrorism/wmd/wmd_fa...
"“(A) any destructive device as defined in section 921 of this title (i.e. explosive device);"
and section 921 has :
"(4) The term “destructive device” means— (A) any explosive, incendiary, or poison gas— (i) bomb, (ii) grenade, (iii) rocket having a propellant charge of more than four ounces, (iv) missile having an explosive or incendiary charge of more than one-quarter ounce, (v) mine, or (vi) device similar to any of the devices described in the preceding clauses; (B) any type of weapon (other than a shotgun or a shotgun shell which the Attorney General finds is generally recognized as particularly suitable for sporting purposes) by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, and which has any barrel with a bore of more than one-half inch in diameter; and "