Purchase, possession, or transportation of firearm; assault and battery of a family or household member or intimate partner; penalties. Adds to the definition of "family or household member," as such definition relates to juvenile and domestic relations district court, a person's intimate partner, defined in the bill as an individual who, within the previous 12 months, was in a romantic, dating, or sexual relationship with the person. The bill also adds to the definition of "family or household member," as such definition relates to a person's purchase, possession, or transportation of a firearm following an assault and battery of a family or household member, any individual who cohabits or who, within the previous 12 months, cohabitated with the person. Finally, the bill provides that any person who knowingly and intentionally purchases, possesses, or transports any firearm following a misdemeanor conviction for an offense that occurred on or after July 1, 2025, for the offense of assault and battery against an intimate partner or an offense substantially similar under the laws of any other state or of the United States is guilty of a Class 1 misdemeanor.