The intent of the Second Amendment is up for debate again. This time the controversy illuminates a modern-age quandary about whether "electrical" weapons like stun guns—or possibly even homemade 3D-printed weapons—are constitutionally protected.

One of the last substantial rulings on weapons came in the Heller case from 2008, when the Supreme Court overturned a District of Columbia statute banning handgun possession in the home. The top court said that such a law violates the Second Amendment, as does the law's prohibition against rendering any lawful firearm in the home operable for the purpose of immediate self-defense. Fast forward to today, following the Heller decision, and every state allows people to carry firearms of sorts outside the home. Some states say OK with or without permits.

But what about electrical arms like stun guns, invented in 1972? Are they covered under this line of Supreme Court reasoning? Currently, that isn't clear.

The Supreme Court is being asked to decide—in a case challenging a Massachusetts ban on the private possession of a stun gun, or a "portable device or weapon from which an electrical current, impulse, wave or beam is designed to incapacitate temporarily, injure or kill...." The challenge before the justices comes in a burgeoning era in which a hodgepodge of weapons are being constructed at home DIY-style and via 3D-printing technology.

The case seeking the Supreme Court's attention concerns Jaime Caetano, who is appealing her 2013 conviction on Second Amendment and self-defense grounds. She claims a right to a stun gun to protect herself from what she said was an abusive father of her children. The penalty for breaching the law carries up to a 2.5-year maximum jail term. She was caught with the device outside a Massachusetts grocery store after allowing the authorities, who were looking for a shoplifter, to search her purse.

Massachusetts' top court, however, said (PDF) the stun gun is a "thoroughly modern invention" without constitutional protection.

Moreover, although modern handguns were not in common use at the time of enactment of the Second Amendment, their basic function has not changed: many are readily adaptable to military use in the same way that their predecessors were used prior to the enactment. A stun gun, by contrast, is a thoroughly modern invention. Even were we to view stun guns through a contemporary lens for purposes of our analysis, there is nothing in the record to suggest that they are readily adaptable to use in the military. Indeed, the record indicates "they are ineffective for . . . hunting or target shooting." Because the stun gun that the defendant possessed is both dangerous per se at common law and unusual, but was not in common use at the time of the enactment of the Second Amendment, we conclude that stun guns fall outside the protection of the Second Amendment.

Ironically, the Massachusetts top court said the woman could have instead applied for a permit to carry a more lethal weapon, like a handgun, to protect her from her abusive former lover.

"Barring any cause for disqualification the defendant could have applied for a license to carry a firearm," the court ruled.

Caetano urged (PDF) the Supreme Court to grant her petition and stated the obvious—electrical weapons like stun guns did not exist when the Constitution was written more than two centuries ago.

"The petition," her attorney wrote the justices, "should be granted so the court can make clear that the 'core' of the Second Amendment is the individual right to keep and carry a bearable instrument—such as a stun gun—for self-defense in case a confrontation, and that this right may exist outside the home."

Constitutional law expert Eugene Volokh and others say the justices should constitutionally protect stun guns. Hawaii, Massachusetts, New York, New Jersey, and Rhode Island, and cities such as Baltimore, New Orleans, Philadelphia, and Washington D.C., all ban the possession of stun guns, Volokh said.

The ability to possess a stun gun instead of a handgun is an important aspect of the right to keep and bear arms. Some people have religious or ethical compunctions about killing. Other religious and philosophical traditions, such as Judaism and Catholicism, believe that defenders ought to use the least violence necessary. Some adherents to these beliefs may therefore conclude that fairly effective non-deadly defensive tools are preferable to deadly tools. Still other people may feel emotionally unable to pull the trigger on a deadly weapon, even when doing so would be ethically proper. Others may worry about erroneously killing someone who turns out not to be an attacker. Still others might be reluctant to kill a particular potential attacker, for instance when a woman does not want to kill an abusive ex-husband because she does not want to have to explain to her children that she killed their father, even in self-defense. Some might fear owning a gun because it might be misused by their children or by a suicidal roommate. Some people who do own guns may prefer to own both a firearm and a stun gun, so that they can opt for a nonlethal response whenever possible, resorting to lethal force only when absolutely necessary. And people who live in states where it is hard to get licenses to carry concealed firearms may choose to get stun guns instead. Yet, under the ruling below, all these residents are denied their right to possess nonlethal stun guns for protection. This is a serious burden on Americans’ Second Amendment rights, and one that merits this Court's consideration.

The Supreme Court is likely to announce as early as next month whether it will take up Caetano's petition.