They've already documented this well:

[url]atf.treas.gov/pub/fire-explo_pub/qa.pdf[/url]

Pg 35


(O8) May law enforcement officers purchase and possess semiautomatic assault
weapons and high capacity ammunition feeding devices?

Yes. The law provides exceptions for law enforcement officers
purchasing assault weapons and magazines for official use. However, assault
weapons may not be lawfully distributed to, or received or possessed by, an
officer having been convicted of a misdemeanor crime of domestic violence. A
licensee may lawfully transfer these items to a law enforcement officer and
the officer may lawfully receive and possess them if:

(1) the officer is a "peace officer" having the authority to arrest
persons for violations of the law and to obtain and execute search warrants;
(2) the officer is employed by a government agency; and
(3) in the case of a semiautomatic assault weapon, the officer has not
been convicted of a misdemeanor crime of domestic violence.

(O9) May law enforcement officers keep their semiautomatic assault weapons and large capacity ammunition feeding devices when they retire or leave their employment with a law enforcement agency?

[b]No. They may not lawfully keep semiautomatic assault weapons and large capacity ammunition feeding devices that they purchased or acquired as their own property.[/b]  However, the law provides an exception for items [i]that belong to a law enforcement agency[/i] and are transferred by the agency to an officer upon the officer’s retirement from, or termination of his or her employment with, the agency. Neither this exception nor the exception for official use permits officers to retain their own weapons or feeding devices after retiring or leaving the agency or to acquire additional items. Officers who retire or leave their employment with a law enforcement agency should transfer assault weapons and large capacity ammunition feeding devices that are their own property to a Federal firearms licensee or another qualified officer.


(019) May a licensed dealer lawfully acquire semiautomatic assault weapons
manufactured after September 13, 1994, remove the features that bring them
within the definition of such weapons in the law, and sell the weapons to the
public?

No. The law prohibits possession of semiautomatic assault weapons
manufactured after September 13, 1994. However, an exception is provided for
licensed dealers possessing and dealing in such weapons that have been
manufactured for and are possessed for transfer to government agencies. A
dealer’s possession of the weapons for sale or transfer to the public is not
among the exceptions to the prohibition on their possession. Thus, a dealer
who acquires such weapons for the purpose of stripping them of their assault
weapon features and selling the modified weapons to the public violates the
law. This is true even if the dealer strips the assault weapon features from
the weapons so that they no longer meet the definition of semiautomatic
assault weapon. The dealer may also have violated the law by making false
statements to a supplier that the weapons were being acquired under an
exception to the prohibition, e.g., for sales to law enforcement agencies or
law enforcement officers.
[18 U.S.C. 922(v), 27 CFR 178.40(c)]
[18 U.S.C. 922(w)(3), 27 CFR 178.40a and 178.119]

(O14) What markings must appear on semiautomatic assault weapons manufactured
after September 13, 1994?

In addition to the markings required of all firearms pursuant to 27
C.F.R. 178.92(a)(1), the frames or receivers for semiautomatic assault weapons
must be marked "RESTRICTED LAW ENFORCEMENT/GOVERNMENT USE ONLY" or, in the
case of weapons manufactured for export, "FOR EXPORT ONLY."

Steve-In-VA has already done so.  We're awaiting an answer.

-Troy