Sorry Folks, but that so called 50 foot distance has never been in any MA law. I was an Natural Resource Officer/ Environmental Police Officer from November 1980 until Jan 2010 and it was never in the abstracts or the statutes. Folks used to spout it, but it was never in the law. I believe this one of those laws or regulations that some other state uses somewhere, that folks thought it meant MA as well, you know like the folks that think because MA requires guns to be locked up that all states require that.
The conspicuously posted issue is that it is accepted that if the property is posted at what is called bar ways, gates or other points of common access then it is "Conspicuously posted".