One of the latest examples comes from Winnipeg [h/t to Brian Ferguson]:
Students at a Winnipeg high school boast on a Facebook site they're running 'black-market' operations out of their lockers — selling pop, chips and chocolate bars banned for sale on school property under Winnipeg School Division's tough nutrition policy....I may be asked to mail in my Libertarian credentials for saying this, but I think the school authorities are doing the right thing. And if I were a parent of students in that school system, I would hope that someone would begin to monitor the Facebook postings and crack down on the black market dealings.
The division adopted the recommendations of a 2005 provincial task force by
banning junk food in favour of salads and wraps in cafeterias, and allowing
only healthy snacks and drinks in vending machines. The policy is aimed at
reducing obesity and related health problems.
But personal views aside, this example is just further evidence that when products are banned, black markets emerge very quickly. After all, people respond to incentives.





If the school is public, it has far greater problem than cafeteria food.
Now, just because the State is paying for my education, it doesn't follow that it's entitled to tell me what to eat (or tell my parents what to feed me).
I saw this documentary from the UK, about this busy-body chef that would campaign to get (public) schools in Britain on a fast-track to nutritional fascism... And the backlash was that mothers would smuggle McDonalds into schools, for their kids.
Regulation is poor substitute for virtue, in most cases.
And in grade school there were several such stores on our way to and from school, in addition to one across the street from the school.
So why the need for a black market to develop in the first place?