The purpose of this paper is to analyse the limits of constitutional reform. Some constitutions, for example, the German (art. 79, sec. 3), the Italian (art. 139), the Portuguese (art. 288), the French (art. 89, sec. 5), and the Brazilian (art. 60, sec. 4), contain an “essential core” of rights, which is usually understood as being immune to change. The initial focus in the paper is on the discussion on whether and to what extent these “essential cores” are indeed immune (...) to change. A second focus is on Ross's paradox. Here I analyse and reject Ross's own solution to the paradox and I show, too, that the paradox admits no solution that does not imply a discontinuity in the legal system. (shrink)