International League Legends of Heroes

You can buy items at levels 1 and 2.
It's the Heroes of Might and Magic market...
The Trade Center isn't a black market, so it's probably not allowed.
And if black markets were banned, they would be banned in the Dungeon and Fortress as well.

It seems like the rules were written by clueless newbies who build a Capitol on day 121 and play with 2-3 heroes until the end of the game.

These are rules for an expert level :D There are also basic and advanced levels :D