I love Walter Williams, but this article makes it clear he is an economist and not a constitutional scholar. Williams wrote:
" They can simply stop wealthy people from leaving the state or,...set limits on the amount of assets a resident can take out of the state. This would surely be within their jurisdiction and would not raise any constitutional issues, because it would serve a compelling state purpose. ...such action would be protected by the 10th Amendment."
The Supreme Court as far back as the 1860s has recognized a fundamental right to travel under the privileges and immunities clause. See, e.g. Paul v. Virginia, 75 U.S. 168 (1869). States cannot substantially impair one's right to ingress or egress from states.