When law-and-economics scholars discuss legal uncertainty, they problematise the use of vague language in the drafting of laws. Here, I would like to contrast that meaning of the term with another. When we say that the law is uncertain, we might mean that two (or more) laws overlap, so that we do not know which is applicable to the facts of a particular case. I call the traditional problem one of applicative uncertainty and the “new” one hierarchic uncertainty. I try to show that the two always coexist, and further that there is a trade-off between them: as the law becomes more applicatively certain, it becomes more hierarchically uncertain.