Vanuatu's Supreme Court Justice, Hamilson Bule, has upheld a government order to deport the Papuan activist, Andy Ayamiseba.
Mr Ayamiseba was deported to Australia last February under the immigration act, which allows for a non-citizen to be deported if the minister rules that the person is involved in activities detrimental to national security.
Lawyers acting for Mr Ayamiseba immediately filed an appeal and got him back into the country on a stay order of the judgement.
His lawyers said the internal affairs minister George Wells acted unfairly and lacked reasonable supporting evidence.
But the solicitor general, Dudley Aru, says the minister made the decision after seeking the opinion of other appropriate authorities.
Justice Bulu upheld the minister's order and said Mr Ayamiseba should be deported as his activities were deemed detrimental to national security and public order.
Mr Ayamiseba has lived in Vanuatu for 20 years on a Vanuatu diplomatic passport.