Traditionally legal theorists, whenever engaged in controversy, have agreed on one point: legal norms are par excellence rules which impose obligations. The author examines this assumption, which from another perspective (that of constitutional law, for instance) appears less obvious. In fact, constitutional rules are commoniy empowering norms, norms which do not create duties but powers. To this objection many theorists would reply that empowering rules are incomplete and that they are to be understood as parts of duty‐creating rules. A different (...) position from this traditional stance is that defended in Kelsen's later writings, according to which the fundamental type of norm is the empowering norm. The author discusses Kelsen's three theories on the “ideal form” or structure of the legal norm, with special attention to the third of these, the empowerment theory. (shrink)