One of the basic principals of the EU is freedom of movement between countries. One could argue that imposing such an onerous tax on moving to another EU country breaks this principal, so maybe worth a legal challenge - for someone with a lot to loose.

Or, alternatively, the bureaucrats in charge would argue that all EU countries need to implement similar exit taxation laws - that's where it seems to be heading lately.

This is why this doesn't apply if you move within the EU.