Cambridge at a guess; where else?
Romney should have censured Cambridge and any other Massachusetts city that declared themselves to be a sanctuary for illegals.
I bet he would in 2007!
It is my understanding that Boston was on the precipice if not officially declared although some of the mentions of Boston that I've heard might have been referring to Cambridge which is part of that metro area.
As far as the governor's obligation is concerned, it really shouldn't matter if it's one city, one suburb or one city block that is refusing to observe federal law.
It would be a great question for the debates ( and therefore won't be asked ): What would you do as president if a city or state declared itself a sanctuary from federal law?