The move by lawyers at the International Criminal Court is likely to enrage Ankara which accused its erstwhile ally Israel of mass murder after the commandos abseiled onto a flotilla challenging an Israeli naval blockade of the Gaza Strip.
"The information available provides a reasonable basis to believe that war crimes under the Court's jurisdiction have been committed in the context of interception and takeover of the Mavi Marmara by IDF (Israeli Defense Forces) soldiers on 31 May 2010," read the paper seen on Wednesday.
But the lawyers decided the crimes in question were not of sufficient gravity to fall under the court's jurisdiction, the papers added.
Prosecutors added they had reached these conclusions on the basis of publicly available information.
"Not having collected evidence itself, the Office's analysis in this report must therefore not be considered to be the result of an investigation," the paper read.
The decision not to open an investigation will disappoint activists who have repeatedly attempted to involve the Hague-based human rights court in the world's most controversial conflict.
The court has no jurisdiction over crimes in Turkey or Israel, since neither is a member of the court. However, one of the vessels, the Mavi Marmara, was registered to the Comoros Islands, which is.
It was the Indian Ocean state that referred the raid to the court, leaving prosecutors no choice under the court's statute but to begin a preliminary examination.
Comoros is represented in the affair by Elmadag, a Turkish law firm, and many critics, especially in Israel, charged Comoros with doing the Turkish activists' bidding by making the referral.
"The Mavi Marmara was deliberately reflagged several days before she set sail," said Nick Kaufman, an Israeli lawyer who represents clients before the ICC. "This allowed the Union of Comoros to be exploited as a jurisdictional vehicle for the continuing and obsessive lawfare against Israel at the ICC."
The Hague-based tribunal was set up to look into the gravest international atrocities, including crimes against humanity and genocide, when local authorities are either unwilling or unable to investigate and try them.
Lawyers represnting the Comoros government said they would apply to judges for a review of the decision not to proceed.
"The Prosecutor's decision marks the first time a State referral by an ICC States Party has ever been rejected by ... Prosecutor without even initiating an investigation," said lawyers Rodney Dixon and Geoffrey Nice in a statement.
"It confirms the view expressed by politicians, civil society organisations, NGOs and commentators from many quarters that Israel has a 'special status,'" they added.
The court declined two years ago to investigate allegations against the Israeli military in 2008-2009, citing the uncertain legal status of the Palestinian Authority, which at the time had not been recognised by the U.N. General Assembly as a sovereign state.