Inspired by the recent activation of the ultra vires review of the Federal Constitutional Court of Germany, the article analyses one of its restrictive elements: the concept of obviousness and its concretization through objective arbitrariness. These concepts are used with good intentions insofar as the ultra vires review requires some conceptualization of deference. But they are incapable of fulfilling this purpose: they disregard the expressive function of law, grant either too much or no deference, and are incompatible with each other. Instead, the substantive standards of structural significance and openness, combined with the procedural rule of unanimity, could serve the purpose of deference in a better and less conflictual way.