Originally Posted By: carp
Does not include bombs, IED's which under 921 would be defined as a destructive device 4 - A,i

Er ... the law the FBI is referencing explicitly includes everything under section 921:

"Weapons of Mass Destruction (WMD) are defined in US law (18 USC 2332a) as:

(A) any destructive device as defined in section 921 of this title (i.e. explosive device);"

Kind of hard to read that any other way ...

I guess they listed explosive this way is because not all chemical and bio WMDs need to use an explosive device.

Well, that, and a big enough explosion just by itself can cause massive damage (see: fertilizer plant, Texas).

The basic problem here is what exactly defines the "Mass Destruction" part of WMD ...