The article is concerned with the question of how legal institutions are structured with the use of constitutive, institutive, consequential, and terminative rules. To that end, the regulation of international treaties as laid down in the Vienna Convention on the Law of Treaties of 1969 is analysed. This leads to the discovery of two additional categories of rules: content rules and invalidating rules. Finally, the special status of unique legal institutions is investigated. Unique legal institutions – for example, heads of (...) state, parliaments, and supreme courts – enjoy validity in a legal system to the exclusion of the validity of any other legal institution of the same category in that system. (shrink)

This paper develops the theory that a set of rules is consistent if it is not possible that (1) the conditions of the rules in the set are all satisfied, (2) there is no exception to either one of the rules, and (3) the consequences of the rules are incompatible. To this purpose the notion of consistency is generalised to make it cover rules and is relativised to some background of constraints.This theory is formalised by means of Rule Logic, in (...) which rules are treated as constraints on the possible worlds in which they exist. Rule Logic itself is introduced by giving a model-theory for it. It is characterised by means of constraints on worlds that are possible according to Rule Logic. (shrink)