The case involves a stun gun, but it was decided squarely on 2a grounds.
In this case an abused woman had been convicted in MA because she had a stun gun in her car, she had restraining orders on her ex). With this decision Supreme Court overturned the conviction, upheld Heller, and said that MA had contravened her choice of self-defense tool.
read the whole decision:
SUPREME COURT OF THE UNITED STATES