[zanny]

> the problem of the wealthy simply moving their wealth out

I could easily see any nation trying to implement higher taxes on the rich to also implement a wealth export tax that takes a tremendous portion of their accumulated wealth if they try to jump ship and take it overseas.

> not bringing it to the high-tax country in the first place.

This is the larger concern, but if a society can't survive without the good graces of the lucky rich, it is already their slaves.