This post is the latest installment of our “Monday Reflections” feature, in which a different Just Security editor examines the big stories from the previous week or looks ahead to key developments on the horizon.

Back in July of this year, I wrote about the decision of the Pre-Trial Chamber at the International Criminal Court (ICC), requesting the Prosecutor to reconsider her decision not to commence an investigation into events around a humanitarian aid flotilla bound for the Gaza Strip, including a ship named the Mavi Marmara, registered in the Union of Comoros. An encounter on May 31, 2010 between the flotilla and the Israeli Defense Forces turned violent, resulting in the killing of 10 passengers, injuries to 50–55 people, and allegations of mistreatment of hundreds of others. At the time, I argued that the Pre-Trial Chamber’s decision risked undermining the “gravity” requirement at the ICC, a provision that is key to the Court’s purpose and legitimacy. I also argued that the Prosecutor should appeal it or, in the alternative, simply consider it and reject it, as is her prerogative under the Rome Statute. Shortly thereafter, the Prosecutor launched her appeal.

On Friday, the Appeals Chamber decided that it would not consider the merits of the Prosecutor’s appeal, concluding that under the Court’s rules, she had no right to bring an appeal in the first place. Why not? The answer turns on the language of the Statute and the nature of the Pre-Trial Chamber’s decision. In the end, although the Appeals Chamber turned back the Prosecutor’s appeal, its reasoning reaffirms the Prosecutor’s power and discretion rather than undermining it.

Back in November 2014, the Prosecutor decided not to start the investigation because she concluded that it would not likely result in a case that could satisfy the Court’s “gravity” requirement, which is included in the determination of whether a case is “admissible” under article 17 of the Rome Statute (the other part of the admissibility analysis being whether the case is already being prosecuted by a state). After the Union of Comoros sought review of the Prosecutor’s decision, the Pre-Trial Chamber asked the Prosecutor to reconsider her decision, which is the most it could do under article 53(3)(a) of the Statute. Then the Prosecutor sought her appeal.

Article 82(1)(a) of the Rome Statute allows the Prosecutor to appeal a “decision with respect to … admissibility.” Therefore, the question for the Appeals Chamber was whether the Pre-Trial Chamber’s request to the Prosecutor constituted such a decision. Relying on prior jurisprudence, as well as the language and structure of the Statute, the Appeals Chamber concluded that the Statute permits an appeal only when there has been a decision on admissibility, meaning a decision that a case was either admissible or not. Because the Pre-Trial Chamber only requested the Prosecutor to reconsider her decision, and there was no decision on admissibility, no appeal is allowed.

There was a path to a decision allowing an appeal, and two of the five judges dissented. But in the end, the majority decision may serve the Prosecutor better than if the appeal had gone through. In its opinion, the majority goes to great lengths to emphasize that despite the Pre-Trial Chamber’s request to the Prosecutor that she reconsider her decision not to investigate, the final decision is the Prosecutor’s and the Prosecutor’s alone: “[T]he Prosecutor is obliged to reconsider her decision not to investigate, but retains ultimate discretion over how to proceed” (para. 59). Without such language, it might be tempting to conclude that a “request to reconsider” was simply a polite way for the judges to order the Prosecutor to start an investigation, and some commentators read it precisely in this way. Not so, said the Appeals Chamber. And by reading the Statute to prohibit an appeal under these circumstances, the Appeals Chamber further emphasized the limited, advisory role of the judges and the determinative role of the Prosecutor.

This decision is also important because it further reaffirms the Prosecutor’s broad control over investigation decisions, a function she is institutionally best suited to perform. The ICC is a relatively young institution, having become operational only in 2002, and therefore the different institutional actors at the Court continue to sort out their relative roles and authorities. The Prosecutor is in the best position to assess situations and cases to make investigative decisions, and the judges should ordinarily grant her considerable deference in this sphere. Elsewhere I have written that the same considerations require that the role of the victims also be limited at the investigation stage, and that they not be permitted to force investigative decisions on the prosecution. A coherent and wise investigation strategy for the Court requires direction from a single actor, the Prosecutor, with a view on all of the cases and the experience to assess the relative merits of potential cases.

Now that the Mavi Marmara decision has come back to the Prosecutor, and for the reasons I provided last July, she should promptly tell the Pre-Trial Chamber that she has reconsidered her decision and has again reached the conclusion that an investigation is not warranted under the Rome Statute. The Prosecutor correctly decided that the gravity requirement will not likely be satisfied on either quantitative or qualitative grounds in this case. The Pre-Trial Chamber’s speculative approach would water down the gravity requirement, forcing the ICC to squander precious resources on investigations that will lead nowhere, undermining the legitimacy of the Court. The Prosecutor has the final say. She should say no.