Er... "It is not for somebody to do" does not necessarily confer rights to someone or something. To me it sounds either like "it is not someone job to do it." or "no one has to do it". However, if you include certain words, like in your example:" it's not for me to tell you what to do", then the meaning changes. It will sound like "it is not my duty (or responsibility) to tell you what to do." In your second example, "it will be for you to decide what action you should take", this sentence means "it is your responsibility to decide on what action you should take". But again, the person's right to do something is only implied... "Duty/responsibilities" and "rights" mean different things. Including these words will make the sentence clearer.