The Supreme Judicial Court of Massachusetts upheld a Massachusetts law prohibiting the possession of stun guns after examining whether a stun gun is the type of weapon contemplated by Congress in 1789 as being protected by U.S. Const. amend. II. The U.S. Supreme Court here found that the explanation the Massachusetts court offered contradicted Court precedent. The Court vacated the judgment of the Supreme Judicial Court of Massachusetts, and remanded.
The Supreme Court has held that "the Second Amendment extends, prima facie, to all instruments that constitute bearable arms, even those that were not in existence at the time of the founding," District of Columbia v. Heller, 554 U. S. 570 (2008), and that this "Second Amendment right is fully applicable to the States," McDonald v. Chicago, 561 U. S. 742 (2010).
The Massachusetts court offered three explanations to support its holding that the Second Amendment does not extend to stun guns. First, the court explained that stun guns are not protected because they "were not in common use at the time of the Second Amendment's enactment." This is inconsistent with Heller's clear statement that the Second Amendment "extends ... to ... arms ... that were not in existence at the time of the founding." The court next asked, under Heller, whether stun guns are "dangerous per se at common law and unusual," in an attempt to apply one "important limitation on the right to keep and carry arms." In so doing, the court concluded that stun guns are "unusual" because they are "a thoroughly modern invention." By equating "unusual" with "in common use at the time of the Second Amendment's enactment," the court's second explanation is the same as the first; it is inconsistent with Heller for the same reason. Finally, the court used "a contemporary lens" and found "nothing in the record to suggest that [stun guns] are readily adaptable to use in the military." But Heller rejected the proposition "that only those weapons useful in warfare are protected." Alito concurred.