> Hence it is legal (in Germany) for politicians to buy/sell right before passing laws which influence the valuation of companies.

Are you sure about that? European legal theory for insider trading implicitly covers more cases than the US without needing to explicitly enumerate them as far as I understand (in a nutshell, trading on insider information is illegal regardless of the source or whether any fiduciary duty was breached), and I'd be surprised if this case were not covered.