The U.S. Supreme Court has refused to hear an appeal by four former Blackwater Worldwide security guards accused of manslaughter in the 2007 shootings in Baghdad that killed at least 14 Iraqi civilians.

A federal judge threw out the case, saying the Justice Department had mishandled evidence and violated the guards' rights. But the U.S. Court of Appeals reinstated the charges.

The high court on Monday refused to reconsider that decision without comment.

The Blackwater guards are accused of opening fire on a crowded Baghdad road in 2007. The prosecutors have said the shooting was unprovoked.

The controversial private security company best known under its former name Blackwater came to symbolize the U.S. policy of hiring private contractors in the Iraqi war to do work previously handled by the military.