Realistic, complex outdoor environments pose significant challenges for node localization in wireless sensor networks. In spite of the fact that many elegant and clever solutions have been proposed, no robust localization system has emerged. This status quo is because existing solutions work well for single sets of assumptions that, however, do not always hold in complex environments. In this article we review the state of the art for node localization in wireless sensor networks and show how localization protocol composability has the potential to provide the robust solution that is needed. By composing localization protocols in a hierarchy and allowing the execution of multiple localization schemes, robust solutions against any single protocol failure can be built.