|DynCorp and Xe Services, the company formerly known as Blackwater Worldwide, have signed the code [EPA]
More than 50 of the world's largest private security companies have agreed to a first-of-its-kind voluntary code of conduct aimed at reining in the firms' worst behaviour.
The International Code of Conduct for Private Security Service Providers, a document whose creation was spearheaded by the Swiss government, was formally signed in Geneva on Tuesday.
It comes in the wake of several high-profile incidents involving private security guards in Iraq and Afghanistan that helped foist the image of mercenaries on much of the industry.
"We are turning the page," said Peter Maurer, the Swiss state secretary for foreign affairs.
"You have to choose whether you are going to be a private security contractor or engaging in warfare."
Among other tenets, the 16-page code of conduct encourages firms to limit their use of firearms to self-defence, not arrest or question people except in limited circumstances, and not engage in cruel or degrading treatment of others.
Two large US firms that operate in the war zones in Iraq and Afghanistan, DynCorp and Xe Services - the company formerly known as Blackwater Worldwide - have signed the code.
The UK's G4 Security, which generates around $11bn in annual revenue, is another notable signature.
The signing ceremony was hailed by Maurer and others in the advocacy and private security communities on Tuesday, but it has received criticism from a high level in the UN.
Jose Luis Gomez del Prado, the head of the UN Working Group of the Use of Mercenaries, has acknowledged that the code of conduct is a "good document" but has also called it "window dressing".
"We need a legally binding instrument. Because what is happening is very serious - it's the privatisation of war," he told the Wall Street Journal newspaper in October.
The code of conduct provides no immediate mechanism by which a firm can be punished for violating any of the agreed-upon rules.
It states that the Swiss government will maintain a public list of all the companies who have signed and will, at some point, convene a conference to review the document.
The code does create a "temporary board" of six to nine members that will arrange an "oversight mechanism" for the companies that have signed on; that board is tasked with creating a plan by the end of March.
Devon Chaffee, a lawyer with the advocacy group Human Rights First, said the document "has the potential to be a monumental step forward".
Even if there is no immediate legal mechanism to hold companies in line, those who support the code in the security industry have said it could be a source of influence on its own, in the way construction and manufacturing companies have adopted international codes.
Under the code, the companies have agreed to minimum standards in recruitment, vetting personnel, and training.
They have also agreed that their employees cannot invoke contractual obligations, orders from superiors or "exceptional circumstances" - such as armed conflict or internal political instability - to involve themselves in any way with torture, enforced disappearances, hostage-taking or other crimes.
Though the private security industry has been expanding for more than a decade, it entered the media spotlight following the US invasions of Afghanistan and Iraq, when foreign governments began relying on security firms to guard embassies, supply lines and aid groups.
Some private contractors have reportedly also been involved in US special forces operations.
Five Blackwater guards were charged with manslaughter in December 2008 in the US for involvement in the deaths of 17 Iraqi civilians in Baghdad's Nissour Square in 2007.
An Iraqi report found that Blackwater guards opened fire on a Kia sedan containing a woman and her adult son after the car did not obey a police officer's order to move to the side of the road.
Blackwater claimed an improvised explosive device detonated near their convoy, which contained State Department personnel, and that they returned fire toward people in civilian and police clothes who were shooting at them.
Those charges have been dismissed by the judge presiding over the case, due to prosecutorial misconduct.
Two other Blackwater guards have also been charged in the US for the killing of two civilians and the wounding of a third in Afghanistan in May 2009.
While Blackwater has been expelled from Iraq by the government there, Xe Services continues to operate in Afghanistan and reportedly in Pakistan.
The company has reportedly been awarded a contract to guard bases in Afghanistan that belong to the US Central Intelligence Agency.