He can come back here anytime. The authorities don’t care about non-citizens entering this country.
It’s the citizens who are prosecuted.
[The 1996 law included a provision to bar entry to any individual “who officially renounces United States citizenship and who is determined by the Attorney General to have renounced United States citizenship for the purpose of avoiding taxation by the United States.” There is no known case of this provision, known as the Reed Amendment, having ever been enforced.]
“1996 HIPAA (Health Insurance Portability and Accountability Act of 1996), H.R. 3103, 104th Congress, page 158” (PDF). Retrieved 2012-05-11.
So, at least theoretically, this guy would be rejected for a travel visa to the US.