Washington: The rules have changed for the hired guns who work on the Defense Department’s payroll.

The rules governing private security contracting firms working in war zones will now cover contractors working in all U.S.-led missions overseas, including humanitarian, peacekeeping or “other military operations” where DoD has boots on the ground, according to an Aug. 1 memo issued by Pentagon acquisition chief Ash Carter.

The memo is an update of DoD rules first issued in 2009. Those only covered contractors assigned to support roles in war zones like Iraq and Afghanistan.

Doing everything from supply convoy support to private security for high-level DoD and State Department officials, PSCs gained a reputation for working outside the accepted rules of engagement of the U.S. military and embodying a gunslinger mentality when out in the field.

After a highly-publicized 2004 attack by Iraqi insurgents in Fallujah, in which four Blackwater operators were ambushed, killed and mutilated, DoD began to take steps to rein in PSCs in country.

Now, under the new rules it does not matter where combat contractors go — whether its Haiti to support U.S. humanitarian missions or to Africa to help out with partner nation engagements — they will have to go through the same oversight process as if they were going to war.

That process requires PSCs to guarantee their training and qualifications meet U.S. military specifications and to get written authorization from combatant commanders to carry weapons

PSC firms must also give details on what they are planning to do in country, how they plan to do it and how it is relevant to the U.S. mission they are supporting — no matter what that mission is

The memo comes at a critical time for U.S troops in Iraq. With the possibility of a small American contingent remaining in country past this year, the role of PSCs could increase.

The guidance also bumps up the level of oversight of PSCs to the deputy assistant secretary level within DoD’s program support office. The 2009 guidance left that job to the assistant deputy undersecretary of the office.

Carter’s office also imposed new rules that would clamp down on PSC operators who use excessive or lethal force when supporting U.S. troops.

The old guidance stated that if a PSC is found guilty of an illegal shooting or some “inappropriate use of force” they would only be subject to “potential” legal action under the status of forces agreement between the U.S. and whatever country American troops were working in.

Now, the new rules are much clearer. If a PSC maims or kills someone unnecessarily, there is a greater chance of legal consequences.

“Inappropriate use of force by contractor personnel authorized to accompany U.S. armed forces may subject such personnel to U.S. or host nation prosecution and civil liability,” the memo states.

PSCs, such as Blackwater and DynCorp International, gained infamy during some of the bloodiest years of the Iraq war. At one point, the number of PSC personnel surpassed the number of American soldiers in country.

In the 2008 Defense Authorization Act, Congress expanded the rules of the uniform code of military justice to cover PSC operations. In 2009, then Defense Secretary Robert Gates issued DoD-wide guidance for combat contractor oversight.