SRS, as a "practitioner of the English language," I agree with you completely. This is the first time I've heard "WMD" applied to anything short of atom bombs, toxic gases, and weaponized pathogens. It goes back to before the days of GWB.

However, the statute in question does define precisely what *it* means by WMD:

http://articles.philly.com/2013-04-24/news/38793219_1_boston-marathon-mass-destruction-weapon

The point may have been that a very general term was required to include whatever might be conceivable. (Just guessing.) Anyway, a jury should be able to tell the difference between a pressure cooker and an A-bomb.