The qualification of private good has to do with whether or not the item is rivalrous (one's consumption decreases the value of another's consumption) and excludable (whether or not you can prevent people from benefitting from your good if you provide it for one person). Private goods are rivalrous, if I consume it, there is less for you. They are also excludable: if I provide one for person A, I can ensure that only person A or anyone person A shares it with consume it. When we say something is provided on the black market, we are just saying that the buying/selling of this item is happening outside of legal parameters.
Chapter 5 Curiosities
Getting Hypothetical...
The cut-off date for posting to this forum is reached so you can no longer post to it.