The 2nd covers arms of the type used by soldiers of the time period as written by the founders. Whe armies were using muskets and cannon civilians could own muskets and some even had cannon.
Trying to use that to justify non-lethal devices could backfire. Next the antis would be arguing that is the only arm you need, and that by only having those non lethal arms your right to arms still exists even with lethal means banned.
There has been a federal law against switchblade knives for decades now. If those are arms why no challenge?, Keep in mind they were banned specificly because some people feared they were prefered arms of some gangs. So they were banned specificly as weapons, or "arms". That would be a place to start if you wanted to broaden the definition of arms.
The 2nd protects "arms", or weapons. Not tools, weapons. So it must fundementaly be a weapon to be an arm. So it must be a weapon to be protected by the 2nd Amendment.
They make comments about the definition when they say things like it is the right of all americans to have every "terrible implement of the soldier".
By the founders definition non-lethal weapons would probably not be considered arms as the purpose of arms was as a lethal tool meant to be a check and balance against power.
For example Tench Coxe put it this way:
"As civil rulers, not having their duty to the people duly before them, may attempt to tyrannize, and as the military forces which must be occasionally raised to defend our country, might pervert their power to the injury of their fellow-citizens, the people are confirmed by the next article in their right to keep and bear their private arms."
Essentialy the rulers may become corrupt and tyrannize, and the military forces which are sometimes required to exist (always exist today) cannot be trusted to never turn against the people or the Constitution, so the people must be capable of taking them on.
So essentialy the very "right to keep and bear arms" was so the government could not impose martial law effectively.
They thought in that context as a result of the Revolutionary War where English civilians organized and broke from the English government they felt were tyrants. They wanted to be sure the population had the future means to resist the government they were creating if it ever became necessary.
In that light the definition of "Arm" would need to be a terrible implement of the soldier, capable of being used against a military force with some effectiveness to be covered by the Constitution.
"...The militia of these free commonwealths, entitled and accustomed to their arms, when compared with any possible army, must be tremendous and irresistible. Who are the militia? Are they not ourselves? Is it feared, then, that we shall turn our arms each man against his own bosom. Congress has no power to disarm the militia. Their swords and every terrible implement of the soldier are the birthright of Americans. The unlimited power of the sword is not in the hands of either the federal or state governments but where, I trust in God, it will always remain, in the hands of the people."
Non-lethal/less-lethal weapons would probably not qualify as "terrible implements of the soldier."
