Changing legal environments create new opportunities for legal mobilization by civil society groups. At stake is mobilization in Germany and Europe for the prosecution of agents of the Syrian Assad regime accused of committing core international crimes. Changes in the legal environment include the (a) spread of universal jurisdiction; (b) increasing use of “crimes against humanity”; (c) new prosecutorial and policing units specialized in core international crimes; and (d) new prosecutorial practices, such as structural investigations. Coinciding with an influx of Syrian refugees, these opportunities give rise to a collaborative network of (I)NGOs that feed witnesses and evidence into prosecutorial agencies. Interaction between agencies and (I)NGOs contributes to the transnational ordering of criminal law and constitutes a Prosecutorial-NGO (P-NGO) Complex. (I)NGOs finally diffuse court narratives to a broad audience and shape public knowledge of grave violations of human rights. We focus on the P-NGO Complex for the al-Khatib universal jurisdiction trial before the Higher Regional Court in Koblenz, Germany. Empirical tools include an analysis of (I)NGO network structures and websites, interviews with court observers, activists, and prosecutorial staff, and an analysis of media reporting.