While it is still considered a crime, it is unlikely that someone would be arrested for it. As far as using it as a grounds for divorce, I would caution you about using it as there are very specific rules regarding the same. Since Massachusetts is a no-fault divorce state, the courts often discourage people from starting a case that way because it does not make a difference when dividing martial assets unless the person has spend marital assets on the boyfriend/girlfriend.
Technically, yes. But, I have not heard of it being enforced as a crime in Massachusetts. Following a vehicle too closely is against Massachusetts driving regulations. But, when is the last time you have heard of that being enforced?
This answer is provided for informational purposes only. Legal advice can only be given in an office appointment by an attorney licensed in your jurisdiction with experience in the area in which your concern lies.
Andrew's answer is correct, but I am wondering if the legality of adultery is really your issue? If you are contemplating divorce, then some people try to make a big issue out of infidelity. Of course, this is an unfortunate situation that can add to the emotions of a case, but conduct issues such as this are frequently not that major of an issue in divorce cases in MA.
Exceptions, of course, exist. If one spouse wastes considerable assets on a new significant other then the other party could seek some adjustments to compensate for the spending of the marital assets.
Hope this helps.
Steve McDonough, Esq.