Looks like MGL c. 266, § 120 is the source here. It does say that as long as the land is "improved or enclosed" and has signs posted, you still can't trespass.

Looks like MGL c. 266, § 120 is the source here. It does say that as long as the land is "improved or enclosed" and has signs posted, you still can't trespass. It's unclear to me if "improved or enclosed" is meant to be exhaustive or is illustrative -- I think that in effect, this would come down to the court's interpretation. https://malegislature.gov/laws/generallaws/partiv/titlei/chapter266/section120 https://malegislature.gov/laws/generallaws/partiv/titlei/cha...