Doesn't stop the problem from flowing the other direction. Often, ex-executives of major firms are now the heads of the regulatory agencies. Do these heads own lots of shares and have obvious conflicts of interest with their 'former' firms? Of course, if your significant other is on the board, well, nothing much the law can say about that either.
The real problem is far too much authority was vested (taken?) by the federal congress. Smaller government is the key to keeping the government in check.