Yup. And they could always get them.
Also, the people who got them generally weren't the most dangerous criminals to begin with anyway. Seriously.

To Scorcese's Eyebrows:
Machine guns CAN be legally owned in the U.S., but there's a stringent background check (applicant pays fee), fingerprints, photos and those who pass must have the license paperwork with the gun at all times.
Crooks like in the movie aren't going to do that, though.

Search the General Laws of Massachusetts
http://www.mass.gov/legis/laws/mgl/269-10.htm
Whoever, except as provided by law, possesses a machine gun, as defined in section one hundred and twenty-one of chapter one hundred and forty, without permission under section one hundred and thirty-one of said chapter one hundred and forty; or whoever owns, possesses or carries on his person, or carries on his person or under his control in a vehicle, a sawed-off shotgun, as defined in said section one hundred and twenty-one of said chapter one hundred and forty, shall be punished by imprisonment in the state prison for life, or for any term of years provided that any sentence imposed under the provisions of this paragraph shall be subject to the minimum requirements of paragraph (a).

It's the same over here in Britain. Lock ya up and throw away the key. Try bringing your dirty guns over here you Yank B##tards.
WHAT'S IN THE BOX??????

When Jackie was talking about life I think he was talking about multiple 10 year counts (X five machine guns).

Yes, Massachusetts has very strict gun laws, among the strongest in the US.