The contribution intends to call attention to an aspect still little investigated concerning the fact that in many cases European administrative law has difficulty in or renounces setting conditions potentially useful for stabilizing the behaviour of administrations and the administered. To that end, the author examines three sets of paradigmatic hypotheses: the first regards cases in which European administrative law operates through sets of rules that can be called ambiguous; the second regards cases in which European administrative law accepts the possibility that functionally-homogeneous administrations may develop divergent behaviour; the third and last concerns some hypotheses in which European administrative law does not guarantee the predictability of administrative action by those to whom it is addressed. In the author's view, the phenomenon represents - depending on the circumstances - a danger or an opportunity: it is a danger when it impedes interactions between administrators and the administrated from giving rise to a rational setup. It is an opportunity when it induces their rationalization. In light of such considerations, the author reflects on the need to rethink European administrative law in terms of a regulatory plan whereby to expand the capacity to operate toward the building of the social order through an action that directly involves not only the political institutions and the administrations of the Union, but also the very theory of administrative law, both Italian and European.