Rebel groups in armed conflicts around the globe are often violators of international law. Yet, out of approximately 350 rebel groups in contemporary armed conflicts, 60 groups issue what legal scholars term “soft documents”—non-binding international law documents with little legal force. Why would some rebel groups express something related to international law, while others don’t? We argue that the soft documents are part of rebel groups’ strategies to improve their political lot. Rebel groups strategically use soft documents to improve the discipline of rank-and-file soldiers, to build up relationships with potential outside supporters, and to disparage national governments. We provide evidence consistent with this logic, using text analysis and regression analysis. Our finding has implications for global security governance—highlighting the motivations of rebel groups in civil conflicts, and rethinking how the international community should engage with rebel forces around the world.