Criminal District Court Judge Raymond Bigelow threw out murder and attempted murder indictments, saying prosecutors had acted improperly, a clerk for the judge's office said.
The police had been accused of shooting pedestrians on the Danziger Bridge in eastern New Orleans on September 4, 2005, just days after Hurricane Katrina inundated much of the city and stranded tens of thousands of people.
Two people were killed and four wounded in the incident, amid widespread looting and shooting. Police officers Robert Falcoun, Kenneth Bowen, Robert Gisevius and Anthony Villavaso were charged with first-degree murder.
Three other officers, Robert Barrios, Michael Hunter and Ignatius Hills, were accused of attempted murder.
All seven men had pleaded not guilty to the charges.
Familes of the victims and their supporters were outraged by the decision, claiming the accused officers received preferential treatment.
More on the story, from the NPR
It's come to be known as the Danziger Bridge incident.
At 9 a.m. on Sunday, Sept. 4, six days after Katrina, police received a Signal 108: Two officers down, under the concrete lift bridge that spans the Industrial Canal.
Seven officers rushed to the scene.
Police say when they arrived, at least four people were shooting at them from the base of the bridge. Officers took positions and returned fire. The official police report identifies two sets of gunmen going up the east side of the half-mile-long bridge.
The investigation hinges on whether these people were the shooters, as the police maintain, or whether they were innocent civilians in the wrong place at the wrong time, as the lawsuits claim.
Three federal civil rights lawsuits were also filed against the officers, though their status is now questionable with the acquittals.
During the incident, the Danziger Bridge was nothing less than a war zone
, though police and civilian eyewitness accounts of what transpired varied widely.