Your example is actually illegal in Steam Over Holland. The percentage of shares sold to the Open Market may not exceed the percentage of shares sold to private investors.
I've only just got this and am just reading the rules (so I may have missed something) but I don't see how this is necessarily an illegal situation. The rules state that a company may not sell more shares than those in the hands of investors on it's turn, but that doesn't seem to prevent it doing so over more than one turn.
Also the shares in the market could have been sold by players I don't see any limit on them selling other than the 50% maximum.