In other words, mere possession means nothing. If they stop you for speeding or something, and find a pick set, they can't do much. On the other hand, if they catch you picking the lock on a Monec machine they get to draw and quarter you.
States with similar wording include ME, NH, NY. One place that DOES NOT have similar wording, and does make possession illegal, is Washington, DC. These are the only other places I have checked. I would imagine that most states are similar to Massachusetts, but I would not bet anything substantial (say, more than a slice of pizza) on it.
It may be a good idea to carry around a xeroxed copy of the appropriate page from your state's criminal code.