I would think that fences would want to discourage people that are actively being hunted by the law from drawing attention to their illegal operations, so it makes sense to me that a black market dealer may tell you to buzz off if your wanted at that station.
Black markets are a place for criminals to sell illegal goods, not a place to hide from the law. That’s what anarchy systems are for.
With that said I’m actually not opposed to wanted commanders being able to access black markets in stations where they’re wanted, but I think it’s riduclous to only make them available to people that have noteriety or are actively wanted as some people suggest. In fact, I think a commander that’s good enough to sneak into a station with a hold full of illegal goods should get better prices from black markets than someone who gets busted on their way in or wanted and drawing unwanted attention to themselves.