Kelsen’s legal monism – the claim that all valid law must, by logical necessity, form part of one and the same system – is often considered to be one of the least convincing aspects of Kelsen’s Pure Theory of Law. This paper will argue that Kelsen’s legal monism is not as indefensible as most commentators tend to think; at least once we recognize the normative basis of Kelsen’s approach to legal and constitutional theory. It will also show that legal monism is not committed to the sovereign state, and that it is therefore wrong to suppose that a move beyond the sovereign state will force us to embrace constitutional pluralism. Legal monism, rather, forces us to acknowledge that the description of law will, in some cases, require a choice between different ideals of legal or constitutional development. In a second step, this insight will be applied to the problem of the unity of European law. It will be argued that Kelsen’s monism can ground a descriptively adequate account of European law while being able to avoid two major shortcomings of constitutional pluralism: the inability to provide guidance in particular situations of legal conflict and the lack of a clear developmental perspective for the European constitution.
