Two years ago this week, seventeen Iraqi civilians were killed by Blackwater guards in Baghdad's Nisour Square. This horrifying incident not only did lasting damage to the relationship between the United States and the Iraqi government but also brought to light the extraordinary dependence of the United States on private security contractors (PSCs) and the lack of legal accountability for these actors.

While the Blackwater guards will finally face trial in January 2010 on charges of manslaughter, the problems with America's use of private contractors continues unabated. Over the past few weeks disturbing reports have surfaced of "lewd behavior and sexual misconduct" by PSCs operating in Afghanistan, as well as unresolved problems with the oversight of contractors working for the State Department. These reports are symptomatic of what has been an overall abdication of responsibility by the US government in overseeing the private companies in their charge.

Over the past 6½ years, the United States has deployed a virtual army of more than 200,000 cooks, support staff, convoy drivers, interpreters, intelligence gatherers and others to carry out the United States mission in Iraq and Afghanistan. None of these private contractors swear allegiance to the Constitution or wear a military uniform and today in Afghanistan - as was the case in Iraq -- there are more of them than actual soldiers. While contractors play an essential and often underappreciated role, questions about legal accountability, oversight and force structure that their presence raises, have remained unanswered.

America cannot continue its dependence on contractors without thinking more strategically about the role they will play in supporting the country's overseas missions. Contractors are now an integral element of national defense and they are not going away. But that's precisely why tough questions and difficult answers about their future roles and responsibilities must be considered - and sharp lines must be drawn.

While the vast majority of contractors are unarmed and engage in often menial work, the presence of armed private security contractors in the battle space raises serious questions of propriety and legal jurisdiction. To date, there is still no legal framework undergirding the use of private security contractors who work for the State Department. Efforts to expand the Military Extraterritorial Jurisdiction Act (MEJA) have languished in Congress and even though then-Senator Barack Obama was the key sponsor of such legislation, his administration has done little to push the issue.

But even with an expansion of MEJA, it would not get to the heart of the issue: quite simply private security guards should not be making often ambiguous life and death shooting decisions in the battle space. Private security contractors can play an important role - they contribute to peacetime operations and even some defensive responsibilities -- but when it comes to personal security or protecting convoys in the midst of war zones the responsibility should lie with public not private actors.

That's why the transition away from their use and the development of government capacity for this function, preferably by military police, must begin immediately. This is particularly true of the State Department, which currently relies on armed guards to protect its diplomats in Iraq and Afghanistan. Yet for all of its dependence on contractors, State Department continues to demonstrate the same problems of oversight year in and year out. According to a recent report by Spencer Ackerman at the Washington Independent the private military company Armor Group was allowed to keep its contract with State even though its guards were unable to speak and understand English - the same issue for which a previous security company had lost a contract.

The problems related to the use of contractors are not restricted to the State Department. While Pentagon oversight has improved, the military needs to do a far better job at integrating armed and unarmed contractors into discussions about force structure and the fulfillment of mission requirements. "Fire and forget" is far too often the mantra when contractors are utilized. Not surprisingly, earlier this year, the head of the Government Accountability Office testified that the Pentagon has yet to do a full examination of its use of contractors; a recommendation the GAO first made three years ago.

This will require institutional-wide changes. For example, each branch of the military should conduct a top-to-bottom review of how that branch interacts with contractors, identify areas for greater or lesser reliance on them and then implement necessary changes.

The dependence on non-state actors, like private contractors, is the new reality of foreign policy in the 21st century - and the use of contractors both in peacetime and during wartime is not going away. If the United States government is to be prepared for this new challenge, the process of acceptance, integration and utilization of contractors can no longer afford to wait.