Mike, I can't answer your direct question. Each city/town can create by-laws that say just about anything. The only people who ever see/read the by-laws are the PD and the city council! They are NOT usually publicly accessible, not on the web, etc. But they are legally enforceable!
I had my run-in with Cambridge by-laws in 1968 and never forgot it! I was working in the PRC (NU Co-Op job at MIT) and got parking tickets for "overtime parking" at unposted/unmetered locations. Called Cambridge PD to be told that Cambridge by-law prohibits >2hr parking unless OTHERWISE posted! I asked him how outsiders were supposed to know this and got a "tough shit" attitude. It was the major reason why I had NU find me a new Co-Op job!
I would suggest giving the owner of Roach's in PRC a call and ask him, he should know if they have a local by-law on it.
As for Boston, the ONLY restrictions that I am aware of (hi-cap, so-called AWBs, etc.) are for RESIDENTS ONLY. According to Chief Ron Glidden (he's talked to Boston's anti-gun office), it does NOT apply to folks traveling in/thru Boston (e.g. my Wife and/or I can carry anything we want on our LTC-A in Boston). Ron also found out that apparently NOBODY has ever been charged with a violation of their by-law. I suspect it was your typical poorly worded knee-jerk reaction by the City Council just before some election cycle.
I don't and wouldn't worry about it unless I lived there (not likely [roll] )!