My statement was from the angle that if you get ripped off in a situation like this, there is no recourse for you, and not legal advice that you cannot get in trouble for participating in these activities.
Probably because that's how it appears to go in regulated markets as well.
It's perfectly legal if it's not specifically regulated as a financial market. Tons of firms do things quite like this - over-the-counter derivatives are rife with various market manipulations.
To me, the whole situation is an incredible demonstration of why "free markets solve everything correctly" is only (even potentially) true as N_participants -> infinity - and even more so a direct lesson in how thoroughly a "market" can fail when it's too small...