First off if you can call in on Monday and say I quit and don't want to come to work today, and you don't goto federal prison, then you are a civilian. Some police think they are not.
In 1968 imported machineguns were banned, in 1986 US manuf. machineguns were banned.
As an individual you can buy a transferable machinegun. This is just a registered weapon not a weapon bought on any license.
Unlike the 94 AW ban where individual officers could buy Assault Weapons on police letterhead and keep them personally. Post 86 machineguns are deptartment owned, and issued to an officer as a duty weapon but they can not keep it.
Someone has to sell and manuf. and demonstrate machineguns to Agencies, so any FFL dealer who pays the SOT special occupational taxpayer can possess post 86 machineguns for demo, sale to govment agencies or to other dealers. Also some security companies have access to machineguns under nuclear or homeland security without being actual govment agencies. Salesmen also possess machineguns so most likely any Glock salesman has a Glock 18 in his posession.
So lots of civilians posses post 86 guns and govment agencies.
If you knew of a FFL SOT dealer you could contact them and be listed on their license as a responsible person, then you could possess, sell, demonstrate any of their shops inventory, so another civilian now has post 86 guns.
BATFE Bureau of Alcohol, Tobacco, Firearms, Explosives. Pay the SOT buy/sell/manuf. beer, Pay the SOT buy/sell/manuf tobacco, Pay the SOT buy/sell/manuf. explosives etc. If you pay enough tax to the government there will be a license available for you to possess the something you desire.