Actually, the general consensus is that the LEO can NOT keep the rifle regardless of configuration.  In fact, we're waiting for BATF to respond to Steve-In-VA's letter to clarify that question.


Regarding LEOs and rifles:

http://atf.treas.gov/pub/fire-explo_pub/qa.pdf

Pg 35


(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.[/b] They may not lawfully keep semiautomatic assault weapons and large capacity ammunition feeding devices that they purchased or acquired as their own property. However, the law provides an exception for items that belong to a law enforcement agency 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.

-Troy