A federal judge in Washington, Ricardo Urbina, has provided another compelling argument against the outsourcing of war to gunslingers from the private sector. In throwing out charges against Blackwater agents who killed 17 Iraqis in Baghdad’s Nisour Square in September 2007, Judge Urbina highlighted the government’s inability to hold mercenaries accountable for crimes they commit.

Judge Urbina correctly ruled that the government violated the Blackwater agents’ protection against self-incrimination. He sketched an inept prosecution that relied on compelled statements made by the agents to officials of the State Department, who employed the North Carolina security firm to protect convoys and staff in Iraq. That, he said, amounted to a “reckless violation of the defendants’ constitutional rights.”

During the presidential campaign, Barack Obama and Hillary Clinton competed over who would take the toughest line against mercenaries. It is clear that the only way for President Obama to make good on the rhetoric is to get rid of the thousands of private gunmen still deployed in Iraq, Afghanistan and elsewhere.

The killings in Nisour Square were hardly the first misdeeds by hired guns in Iraq, or the last. The army has said contractors from firms like CACI International Inc. were involved in more than a third of the proven incidents of abuse in 2003 and 2004 in the Abu Ghraib prison. Guards from Blackwater  which has renamed itself Xe Services  and other security firms, like Triple Canopy, have been involved in other wanton shootings.