International law has a thriving critical scene, arguably bigger and more institutionally established than any other field. Yet political economy has been an unstable point of focus for critical international lawyers, in part because the justifications of the status quo in the international domain never coalesced into anything akin to a ‘21st-century synthesis.’ This picture of fragmentation and instability helps explain why Marxism provides a useful set of intellectual tools for approaching law, in particular, and social formations in general.