Knowledge and Information distribution, which is one of the main processes in Knowledge Management, is greatly affected by power explicit relations, as well as by implicit relations like trust. Making decisions about whether to deliver or not a specific piece of information to users on the basis of a rationally justified procedure under potentially conflicting policies for power and trust relations is indeed a challenging problem. In this paper we model power relations, as well as delegation and trust, in terms of an argumentation formalism, in such a way that a dialectical process works as a decision core, which is used in combination with the existing knowledge and an information distribution system. A detailed example is presented and an implementation reported.