Legal Question in Real Estate Law in Massachusetts

It depends on the context, but generally, it is considered a request based on a rule and as such can be viewed as a requirement. For instance, in a library the term "please refrain from using cellphones" is a request, but the implication is that you are not supposed to use a cellphone in the library and they can ask you to stop.

In other words. it is a gray area and is subject to interpretation based on context.