Analysis published by Just Security, which is pro-application of international law and as far as I know doesn't have any apparent stake in its non-application in this case, suggests that the decision not to prosecute based on the gravity standard is consistent with previous ICC precedent.
I think this is important because some people are saying that the court reflected a pro-Israel bias in deciding not to prosecute.
I don't have any particular interest in defending the ICC, even from unjust criticism; I don't personally like the ICC that much overall; in particular, I think the prioritization of prosecution over peace implicit in the Rome Statute is a fatal flaw. But I fear that the apparently false claim that the ICC decision in this particular case was motivated by pro-Israel bias could have a side effect of mis-educating people about the ICC in a harmful way, suggesting that it is more susceptible to political pressure from the big powers than it is (which, obviously, it is to a significant degree.)
This could lead people to think, for example, that there is no point to Palestine joining the Rome Statute because a prosecution of Israel will never be allowed. I think that a more careful reading of this case suggests that is not necessarily true. This case suggests that neither Israel nor anyone else will be prosecuted by the ICC for a "small" crime in scale. But it does not suggest that, for example, Israel could not be prosecuted for its settlement policies in the West Bank or for anti-civilian collective punishment actions related to the Gaza blockade or for large-scale war crimes during future wars.
Also, it is worth noting that under the Rome Statute a preliminary, open-source investigation of the case was mandated by statute following the complaint, even if it was clear what the result would be. My guess is that the Mavi Marmara lawyers knew what the result would be, and have seen this as a media-political strategy all along: their goal has not been necessarily to win a legal case, but to take advantage of every possible venue to generate criticism of the Israeli government's actions in the raid that will generate international press coverage. This seems like a perfectly reasonable strategy to me. It's like asking for a CRS report. It's some form of accountability.
Here are some key documents:
Breaking News: ICC Prosecutors Decline to Investigate “Freedom Flotilla” Incident http://justsecurity.org/17141/breaking-news-icc-prosecutors-decline-investigate-freedom-flotilla-incident/
ICC Analysis on the Flotilla Incident–Fair & Balanced? http://justsecurity.org/17183/icc-analysis-flotilla-incident/
Statement of the Prosecutor of the International Criminal Court, Fatou Bensouda, on concluding the preliminary examination of the situation referred by the Union of Comoros: “Rome Statute legal requirements have not been met” http://www.icc-cpi.int/en_menus/icc/press%20and%20media/press%20releases/Pages/otp-statement-06-11-2014.aspx
Here is a bit of press:
Reuters: ICC says won't probe Israeli raid on Gaza-bound flotilla International prosecutors believe Israeli soldiers may have committed war crimes during the 2010 raid, but these offenses were not of sufficient gravity to fall under the court's jurisdiction. http://www.haaretz.com/news/diplomacy-defense/1.624955
International court will not prosecute Israel in aid flotilla case http://www.latimes.com/world/middleeast/la-fg-israel-gaza-court-20141106-story.html
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Robert Naiman Policy Director Just Foreign Policy www.justforeignpolicy.org naiman at justforeignpolicy.org (202) 448-2898 x1