As a "militiamen" who may some day have to fight not only invaders, but possibly ones own government, ANY weapon that could be used to do so is fair game. A nail file, a zip gun, an M-134D mini-gun, a Howitzer 105mm.
To say that "government" may define what is and is not a "militia" weapon could have us fighting our own government with little more than squirt guns and harsh language.
Most definitely NOT what the Founders intended.
The state would decide, not the federal government. If your state Militia used soda cans as weapons, and if Congress banned soda cans, your state could contest that as a second amendment infringement.