There's always a way. No matter what crap one lawyer can conjur up, some other lawyer can find a loophole.
A few years ago, while browsing around the local Orvis shop, I found a nice old depression-era SxS 12ga shotgun in the rack and decided to buy it. The salesman said, "Sure thing, but we have to take a walk first." HUH? He led me out the door and about a block down the street to a different building. We went inside, filled out the 4473 form, did the background check call, I forked over some cash, and we concluded the sale. Then we walked back to the Orvis shop and I picked up my gun.
It seems that his FFL listed the other building as his business address so, legally, he had to conduct the sale there.
I can see the fuel businesses making "the sale" and collecting money across the street or in the parking lot or somewhere to get it out of the FBO.
Or...
"Hey, buddy. I can't sell 100LL at this airport, so pull your plane up next to the airport fence. I'll park the fuel truck along the street and snake the hose over the fence."
This could get entertaining.