Lawyers for hate preacher Abu Hamza today argued he should keep his British passport because he has been stripped of his Egyptian nationality.
The radical cleric is appealing against an attempt by the Home Office to take his passport away from him.
At a hearing before the Special Immigration Appeals Commission (Siac), Hamza's lawyers are arguing he has been stripped of his Egyptian citizenship so cannot have his British passport taken too, as that would render him "stateless".
But the Home Office says there is no documentation to prove he is no longer an Egyptian national and though he was once denied an Egyptian passport, he was later allowed one.
At the start of a three-day hearing in central London today, the commission heard 52-year-old Hamza may have had his Egyptian nationality revoked but the country's government would not confirm whether he had or not.
The cleric came to Britain on a student visa and acquired a British passport through marriage.
He was denied an Egyptian passport in 1982 because he had not undertaken military service, the panel heard, but a decree in 1988 allowed him his citizenship back.
But Egyptian law expert Sabah Al-Mukhtar, appearing as a witness for Hamza's legal team, told the commission it was possible he had been stripped of his nationality later on for other reasons.
He said by refusing Hamza a passport the Egyptian government was giving a "de facto" denial of his nationality.
The panel heard that under Egyptian nationality laws, a citizen cannot obtain a foreign nationality without government permission.
If they do, that nationality may not be recognised by the Egyptian government.
And today Mr Al-Mukhtar said his interpretation of the law was if an Egyptian obtained a foreign nationality without permission, they would be stripped of their Egyptian citizenship.
He said: "There must be a sanction. That could be one of two things - either to treat the acquired nationality as invalid or to lose the original nationality - otherwise it becomes a meaningless provision."
But James Strachan, for the Home Office, said this interpretation was a "fundamental disagreement" with their expert's evidence.
He said Hamza had travelled to Egypt using a British passport and had been granted a visa to visit the country.
"None of these events require or mean that he has been stripped of Egyptian nationality.
"The 1988 decree demonstrates conclusively that in fact the appellant was granted permission to obtain British nationality and to retain his Egyptian nationality," he said.
Mr Al-Mukhtar replied: "At that date absolutely, what happens after that is another matter."
The panel heard decisions of people having their nationality taken from them were usually published in the country's "Official Gazette.
Mr Al Mukhtar said: "I have not seen any decision of the Government to stop him but I am suggesting to you that the government does not actually, despite what we have said, need to announce it.
"If that decision 1988 had a fault in it then it becomes invalid, then the government does not have to do anything about it."
But the expert admitted some of his report was based on speculation as well as Egyptian law.
"In my experience this is one of the few cases where I am being asked to give advice on speculation rather than facts," he said.
"Because the Egyptian government would not answer the straight question as to whether he has or has not got a nationality we had to get the experts in."
Hamza, who was jailed for seven years in February 2006 for inciting murder and race hate, is in Belmarsh Prison as he challenges attempts to extradite him to the US on terror charges.
That case was delayed by the European Court of Human Rights in Strasbourg in July, which called for further submissions over the length of his sentence and the conditions he would experience if extradited to ADX Florence, a so-called "supermax" prison in Fremont County, Colorado.
Attempts to take his passport away were launched in 2003 but delayed by other legal actions against him.
The Siac hearing, scheduled to last three days, was adjourned until tomorrow at 10.30am when Mr Al-Mukhtar is due to continue giving evidence, as well as Hamza himself.