When most of us think of weapons of mass destruction, we think of nuclear bombs, or nerve gas, or biological agents. So it was surprising to see accused Boston Marathon bomber Dzhokhar Tsarnaev charged with using a weapon of mass destruction after he and his brother allegedly detonated a bomb made from a pressure cooker.

Heinous as the Boston bombing is, a pressure cooker does not fit the commonly used definition of a WMD. In fact, by its own definition, the U.S. government is using WMDs every day. There appear to be two relevant laws here. The first is found in Title 18 USC § 2332a, which defines weapons of mass destruction as

(A) any destructive device as defined in section 921 of this title;

(B) any weapon that is designed or intended to cause death or serious bodily injury through the release, dissemination, or impact of toxic or poisonous chemicals, or their precursors;

(C) any weapon involving a biological agent, toxin, or vector (as those terms are defined in section 178 of this title); or

(D) any weapon that is designed to release radiation or radioactivity at a level dangerous to human life;

So far, so good. Beneath the legalese, this mostly fits the common definition of WMDs. However, Section 921, the part that defines WMDs as destructive devices is where the law gets interesting. For purpose of a WMD, a destructive device is defined as a

(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;

or, 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.

Now we have a problem. By this standard, the U.S. military is using WMDs every day, and could be prosecuted by a foreign power if they were to adopt similar laws. Here are a few examples:

M67 hand grenade: U.S. military’s fragmentation grenade is a grenade under Section 921, and it has an explosive charge of 6.5 ounces, so it qualifies as a WMD on two counts.

TOW-2 anti-tank missile: The TOW-2 is a rocket that blasts through tank armor with a 13-pound warhead, which would qualify as a WMD. Note that a  U.S. Army veteran was charged [http://articles.washingtonpost.com/2013-03-28/world/38099269_1_affidavit-al-nusra-syrian-rebel-group] last month by the FBI with using WMDs after he fired Russian-made rocket-propelled grenades while fighting in Syria alongside the rebels.

M795 artillery shell. The U.S. military’s standard 155-millimeter howitzer shell carries 20 pounds of TNT to its target. This would appear to qualify it as a weapon of mass destruction.

PGU-14/B Armor Piercing Incendiary ammunition – These tank-killing rounds for the 30-millimeter cannon on the A-10 Warthog attack jet use depleted uranium (an extremely dense metal) to punch through armor – and releases radiation in the process. The Pentagon has maintained for years that the radiation is too small to be dangerous, but some – including Desert Storm veterans [http://www.gulfwarvets.com/du.htm] have argued otherwise.