Since its publication in 2000, Hardt and Negri's book Empire has been at the centre of significant debates within international relations (IR) and international law (IL) communities, both academic and other. Hardt and Negri's recently published Multitude (2004) is likely to add momentum to these debates. Outlining the importance of both Multitude and Empire for legal scholarship and practice, this contribution sets out to give a brief overview of the core issues that are to be distinguished in the debates amongst IR and IL academics, and includes a number of criticisms that could be levelled at Hardt and Negri's work. The focus of the paper, however, is on the ambiguities that mark Hardt and Negri's flawed attempt to deal with the issue of the boundary of Empire and the liminality of (the) multitude. Indeed, this contribution maintains that precisely this rather fundamental flaw in Hardt and Negri's work is why their intellectual ‘tour de force’ is ultimately unconvincing.