According to Mashable, the first person to go to jail for making a 3-D printed firearm was a 28 year old man from Japan, Yoshitomo Imura. Read more about the story here.
In Japan gun ownership is heavily restricted and there is no exception for 3-D printed guns, though the arrested man claimed he didn't understand he was breaking the law.
In Massachusetts, a 3-D printed firearm will be treated like any other firearm manufactured in your home. Just because the technology has made it easier for more people to manufacture firearms doesn't change the legality of doing so. For more on that subject, and to avoid ending up like Mr. Imura, check out our recent post: Is Making a Firearm in Your Home Legal?