I don't think there is a FAA reg specifically stating that you can't PUT jet fuel into anything but an airplane but all the FBO's at SLC International hold to that policy. Pre-9-11 I could buy Jet A from the International airport but since then they have really tighened their belts. They gave me the "it has to go in an airplane" shpeal so I said I'd bring in my Hot Spot and have them fill it 5 times.
After that they let me talk to the manager and he let me do it and really thought my planes were cool. Their latest excuse is that there's some haz mat regulation that prevents it.
If you're having trouble getting Jet A from one airport, go to another. Chances are the smaller the airport the more likely you'll be to get what you want. To solve my problem I just drive 15 minuets farther to a smaller airport that sells it to me no questions asked.