A 29-year-old man is stateless in Hong Kong after he was stripped of his Belgian nationality.

Sze Chung Cheung, who has lived and worked in Hong Kong since 2009, was born in Hong Kong to a Belgian mother and a Hong Kong father.

The financier's problems began in February when he applied for what he thought was a routine passport renewal.

He was shocked to be told by a Belgian consular official that he was no longer Belgian because of a little-known clause in the country's citizenship law.

"I did not think that it was possible for me to lose my nationality unless I betrayed my country or was guilty of great crimes," he said.

Ever since then, Sze, who lives in Tseung Kwan O, has been fighting an uphill battle to reinstate his nationality.

"For a long time I thought I could come to an agreement with Belgium, which sounds like some kind of dream or wishful thinking," he said.

Sze was told by Deputy Consul Paul de Vos that he had lost his citizenship because he had not met certain criteria under the Act of Belgian Citizenship: he was not born in Belgium, he did not live in the country between the ages of 18 to 28 and he did not state his intention to retain his nationality before the age of 28.

"This law should not have been applied to me because all my life I have only had Belgian nationality," said Sze, who holds a permanent Hong Kong ID card.

"What the consulate has been telling me [is that it] … seems obvious 'in our view that you are of Chinese nationality'. I was guilty without proof."

Patrick Wautelet, a professor of law at the Université de Liège in Belgium who specialises in cross-border nationality issues, said officials had no requirement to inform people about risks to their citizenship.

"It would be counterproductive," he said.

Citizenship lawyer Barry Chin Chi-yung said that a Hong Kong identity card "cannot alone indicate that a person is a Chinese national".

Six months after Sze was born in 1984, he was registered with the consulate in Hong Kong. At age two he moved to Brussels with his parents. Later, the family relocated to France and in 2009 he moved to Hong Kong.

Throughout his life, Sze has travelled as a Belgian citizen with his Belgian passport.

Evert Marechal, Belgium's consul general for Hong Kong, said the consulate did not comment on individual cases, citing "privacy and confidentiality".

He said Sze could reapply for his nationality by working in Belgium for a year or obtain a visa for a Hong Kong passport.

"How can I just move country, find a new job? Do I want to do it? My life now is here. This condition now makes me unable to fulfil it," said Sze.


Pair who lost Belgian citizenship needed 7-year court fight to get it back

In 2013, after a seven-year legal battle, Belgium's second-highest court, the Court of Appeal, ruled that the government's decision to strip lawyers Marc and Louis Ryckmans of their citizenship was unlawful.

The Ryckmans twins – born in 1967 in Hong Kong and the sons of Belgian-Australian writer Pierre Ryckmans (Simon Leys) – were registered with the consulate in Hong Kong. The family moved to Australia in 1970. Both obtained their first passports in 1985, and continued to travel on Belgian passports until 2006, when their request for renewal was refused. They were asked to make a declaration to keep their Belgian nationality if they also possessed another one. They did not make a declaration.

Diplomats in Sydney argued that the Ryckmans were Chinese nationals through their mother. Later, officials argued the Ryckmans were British citizens, since they were born in Hong Kong.

The Court of Appeal judge focused on why the identical twins had not made a declaration of their nationality. According to Belgian legal scholar and expert Patrick Wautelet, the twins "were entitled to believe they did not possess any other nationality than the Belgian nationality".