Lawyers representing extremist cleric Abu Hamza say he will become 'stateless' if the Home Office strip him of his UK passport.
Hamza, 52, came to the UK from Egypt in 1979 on a student visa and acquired British citizenship through marriage.
This was subsequently withdrawn in 2003 by David Blunkett after he praised the September 11 attack on the World Trade Center in Manhattan.
He was then jailed in February 2006 for inciting murder and racial hatred, and is currently residing at Belmarsh Prison midway through a seven-year sentence.
He is also fighting an attempt to extradite him to the United States to face terrorism charges.
At a hearing of the Special Immigration Appeals Commission in central London this week, Hamza's lawyers argued he should not have his British passport taken away since he has already been stripped of his Egyptian citizenship.
The Home Office, however, says there is no documentation to prove he is no longer an Egyptian national.
While it is acknowledged he was denied an Egyptian passport in 1982 for failing to undertake military service, a national decree in 1988 allowed him his citizenship back.
Hamza's lawyers dispute this. They say the 1982 refusal was a "de facto" denial of his nationality. Egyptian legal expert Sabah Al-Mukhtar told the tribunal that under Egyptian nationality laws a citizen cannot obtain a foreign nationality without government permission.
If they do, he said, one of two things could happen: either the government will treat the acquired nationality as invalid or strip the citizen of their original Egyptian nationality.
The hearing is scheduled to conclude today.