If I have my facts straight, a LE Demo letter is in regards to a Post-1986 full-auto weapon. Only military and LE can own such weapons and a letter of intent/request for evaluation must be submitted to the dealer before the firearm can be transfered. I guess the intent is to keep people from becoming dealers and buying post-86 guns to use for themselves.... they can't order the guns without an LE request.
No, it's not something a civilian can do.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.