The United States must stop relying on mercenaries in Iraq.

The Sept. 16 incident in Baghdad, where Blackwater USA, a private security company, killed at least 11 Iraqi civilians, has created a diplomatic crisis between the United States and Iraqi governments.

Worse, it has made a mockery of U.S. efforts to establish democracy in the country it invaded more than five years ago. Iraqi Prime Minister Nouri al-Maliki has already called for Blackwater to cease operations, saying the mercenary army amounted to a challenge of his nation’s sovereignty.

While initial accounts of the incident said Blackwater was responding to gunfire, subsequent Iraqi reports claimed that there was no attack. Instead, they said Blackwater security guards opened fire at a car that didn’t stop when told to by a policeman, and its passengers – a couple and their infant – were killed.

Blackwater, which is the primary provider of security to senior U.S. officials, including Ambassador Ryan Crocker, operates outside the law and governmental supervision. Having received a no-bid contract and operating on billions of dollars in taxpayer funds, Blackwater plays the role of renegade cowboys, flying low in helicopters with guns drawn. It is despised by Iraqis, and even some U.S. military personnel.

This is not the first time that Blackwater operatives have been involved in serious incidents in Iraq. The Iraqi government has announced it is investigating five previous incidents that occurred earlier this year in which 10 Iraqis were killed and 15 wounded. Last Christmas Eve, an off-duty Blackwater contractor allegedly killed a bodyguard for the Iraqi vice president.

The reckless use of Blackwater greatly undercuts the moral authority of the United States as a beacon of democracy, and calls into question the true extent of Iraqi sovereignty. How can the U.S. claim to be bringing freedom and democracy to Iraq while imposing a mercenary army on an Iraqi government that is not empowered to prosecute it?

Blackwater’s role in maintaining security is so crucial that its removal presents a logistical nightmare. That, in itself, shows how reliant on mercenaries the United States has become.

This practice should end now, and those responsible for civilian deaths should be brought to justice.