This kind of thing has been reported before.
Never had chacneg to fully look in to it. However, for a few months I was making a list of black market that I have visited, about 80 at the time. I later returned to list with the intention to sell ileglla goods. Some black market seemed to have gone. It mya have been errors in my list.
I did another experiment with a freshly terraformed system. It had two stations, the new one, low population and no goods apart from hydrogen fuel and bio-poop, with a black market and where weapons were illegal.
Also in the system was a outpost that sold guns. So myslef and some others ran guns between the two systems. Eventually the weapons became legal at both stations and I think the black market may have gone. My memory of it all is vague.
Here's the original thread.
https://forums.frontier.co.uk/showthread.php?t=121388&highlight=Djaujas