There's a legal process to renounce citizenship of ones native country.
The united states in particular is reported having record numbers of citizens renouncing citizenship in 2016.
A record number of Americans abandoned their US citizenship last year, according to official figures.
Statistics published by the US Federal Register showed that 5,411 people gave up their nationality, an increase of 26 per cent on 2015.
For many the main motivation is tax.
Americans are liable for US tax even if they live abroad. Although in most cases they are unlikely to face a bill because they can offset what they pay to the taxman in their country of residence.
However high earners can face a bill from the US Internal Revenue Service even after they have paid substantial taxes to the Government in their adopted country.
In addition they are expected to file a US tax return every year, irrespective of what they earn.
Americans living abroad are also taxed on any profit they make on selling their home when they live abroad, even if they have no intention of ever living in the United States.
New laws passed in 2010 made life even more difficult for American expatriates.
The Foreign Account Tax Compliance Act - or Fatca for short - requires banks to declare savings held by US citizens to the American tax authorities. This requirement, which applies to Americans living abroad, has led some banks to refuse to open accounts for US expats or threaten to close them down.
Those giving up their US nationality include “accidental Americans” who were deemed to be citizens because they were born in the United States, even if they lived their entire life elsewhere.
Boris Johnson, the Foreign Secretary who was born in New York, is among those to have renounced their US citizenship.
http://www.telegraph.co.uk/news/2017/02/11/number-americans-renouncing-citizenship-reaches-record-high/
I would guess that citizens of Vanuatu could renounce their native citizenship to avoid paying taxes, although I think they have made it more difficult in recent times for people to do this.