Australian terror suspect Mamdouh Habib has arrived back in Sydney after being released from Guantanamo Bay. U.S. officials said they didn't have enough evidence to charge the former taxi driver with terrorist offenses. The Australian government has insisted that Mr. Habib trained with al-Qaida and had prior knowledge of the September 11, 2001 attacks in the United States. After four years in detention - most of them at the U.S. base at Guantanamo Bay, Cuba - Mamdouh Habib has arrived home. Australian Foreign Minister Alexander Downer said in a statement that Mr. Habib had been reunited with his family. He has returned a free man, but his movements are likely to be severely restricted. He will face close surveillance by Australia's security agencies and almost certainly will not be allowed to leave the country. Australia has given the United States a guarantee that Mr. Habib will no longer pose a terrorist threat. Mr. Habib's lawyer, Stephen Hopper, says he faces a lifetime of being followed by the authorities. "It's completely unnecessary," he said. "Mr. Habib has been under a lot of scrutiny for the last nine years and they haven't been able to get an atom's weight of evidence against him, and the only supervision that he'll really need is provided by his wife, Maha. She's not going to let him put a foot out of line after what she's gone through." Unlike four British terror suspects released from U.S. custody at Guantanamo Bay earlier this week, Mr. Habib was not arrested on his return home. Officials in Canberra said he would not be charged because it had not been an offense in Australia to be involved with the terror network al-Qaida at the time of his detention. The law was changed the following year, but is not retroactive. Mamdouh Habib was detained in Pakistan in 2001, three weeks after the attacks in New York and Washington. He was accused of training with al-Qaida and was held in custody in Egypt for a time. He has claimed he was tortured for six months in Egypt before being sent to Guantanamo Bay, where he was held without charge. Another Australian being held in Guantanamo Bay is expected to face a U.S. military tribunal later this year. David Hicks, a former kangaroo hunter, has been accused of conspiracy to commit war crimes, attempted murder and aiding the enemy. He has denied the allegations.