Three Africans claiming refugee status won permission to mount a challenge in the top court yesterday.
They will fight a ruling that the government is not bound by an international principle that a person should not be returned to a place where his safety might be in peril.
The three also want to overturn a court ruling, affirmed by the Court of Appeal last year, that the government has no obligation to screen claims for refugee status and can instead pass them to an international institution.
The claimants were among six seeking refugee status who lost a 2008 judicial review into whether or not the government had followed the universally accepted practice under international law of not expeling people who have a well-founded fear of persecution. Their case was that it had not.
The Court of Appeal yesterday granted the three permission to argue the case in the Court of Final Appeal on the grounds of its great public importance. The top court will have to clarify whether the principle of non-refoulement, or non-return, is a compelling international law or norm and whether it has been excluded from Hong Kong law.
The Court of Appeal last year upheld arguments that the Director of Immigration had full discretion to decide whether to expel a claimant to refugee status.
It ruled that Hong Kong, which is not a signatory to the United Nations Convention Relating to the Status of Refugees, was not bound by the principle of non-refoulement.
If the top court rules the principle is not excluded from domestic law, the judges will also answer the question of whether the government is obliged to conduct its own inquiries into claims for refugee status.
At present, the Director of Immigration refers such claims to the United Nations High Commissioner for Refugees.
If the commissioner accepts a claim is genuine, the government gives the applicant temporary refuge in Hong Kong until he or she is accepted for resettlement overseas.
If the claim is rejected by the commissioner, the director will deport the claimant, although he may exercise his discretion not to expel an applicant for humanitarian reasons.
The application was made before Mr Justice Andrew Cheung Kui-nung, Madam Justice Maria Yuen Ka-ning and Mr Justice Johnson Lam Man-hon.
The government has a firm policy of not granting refuge and asylum because Hong Kong is small and densely populated and vulnerable to abuses of such claims.
China has been a signatory to the refugee convention since 1982.