This paper addresses the counterhegemonic potential of rights constitutionalism in the age of globalization, and in particular its capacity to respond to the rise of significant forms of private power. It locates this issue in the context of the paradigmatic debate of modern law between liberal legalism and legal pluralism. The latter challenges the core epistemological assumptions of orthodox constitutional thought that law is exclusively state law (by positing the existence of non-state legal orders) and that this tends towards coherence and effectiveness. For legal pluralism, constitutionalism's importance does not lie primarily in the outcome of normative argument, but in symbolic terms as a legitimating discourse. Accordingly, to claim that law only emanates from state institutions, and is an effective tool of social engineering, is not simply an analytical statement, but reflects a substantive political agenda. The politics of definition of classical liberalism and the 'new constitutionalism' are contrasted to consider how they set the parameters for political debate. The former, which views constitutionalism as negative limits on the state, reinforces hegemonic interests by its narrow conception of political power as inhering in public institutions, whereas the latter, by locating constitutional norms, for example in the actions of multinational corporations, potentially opens up private power to constitutional scrutiny. It is concluded that the prospects for counterhegemonic constitutionalism lie in opening up the politics of definition of constitutional law to critical debate.