You guys are making a lot of noise about something you know nothing about.
Phaser, I feel for ya buddy but the host nation agreements are very specific about who can buy on-base goods and services. This is because all that stuff enters the country without import tariffs and is sold without any host nation taxes on the retail end. Abuse of the BX/Commissary system used to cost the local govt millions of bucks every year and there is still a thriving black market of authorized tax-exempt customers who buy their quota on base and turn around to re-sell it outside the gate.
In the UK, the biggest issue is gasoline. It's such a problem that not only did they clamp down on off-base gas ration cards, they also tried to monitor how much people were buying on base. In Korea, they have limits on EVERYTHING, including ground beef, rice, etc. If a single person buys more than about 20 lbs of steak in a month for example, or tries to buy more than a couple pounds of beef in one shopping trip, it'll flag their account and they may get investigated.
Again, it's NOT arbitrary or BS, it's the only way to cut black marketing in accordance with host nation agreements that have been in place for decades, even if they were not always enforced in the same way.
I think there ARE ways to get authorized use of on-base support on a temporary basis, but you'd need to find the exact right person to talk to and catch them in a good mood. I think the support group would be the place to check, but I'm not sure. I am pretty sure that people in the country on a tourism visa or conducting personal business are generally not authorized, but again I remember hearing about exceptions when I was in the UK so you'd have to find out exactly what the categories of authorized users are, and get a ration card or your ID entered into the ration system, however they happen to be doing things in that particular location.
Edit - Airscrew seems to be on the right track. It's a question of finding out if you fit within the right category and then filling out paperwork.
In Korea, even though I was serving an unaccompanied tour, my wife could show up and get a limited use ration card so she could even get in the door at the BX... But there were rules to follow and paperwork to fill out.