Why is a pressure-cooker bomb a "weapon of mass destruction" but

[neverforget]

32. Apparently an RPG is a weapon of mass destruction

Thirty-year-old U.S. Army veteran Eric Harroun was charged Thursday with violating U.S. law by fighting with Syrian rebels to depose Bashar al-Assad.

Harroun was charged with "conspiring to use a destructive device outside the United States" after telling FBI agents that he used rocket-propelled grenades against Syria's military. Harroun entered Syria in January and ultimately joined up with Al Nusrah fighters, which the U.S. says are aligned with al-Qaida. He boasted about his war exploits on Facebook, including the downing of a Syrian government helicopter.

An affidavit drafted by FBI agent Paul Higginbotham reads: "There is probable cause to believe that, in or about January 2013 to March 2013, Eric Harroun conspired to use a weapon of mass destruction, i.e. a Rocket Propelled Grenade, outside of the United States, in violation of 18 U.S.C. 2332a(b)."

http://www.usnews.com/news/newsgram/articles/2013/03/29/fbi-affidavit-us-army-vet-used-weapon-of-mass-destruction-in-syria