Voluntary euthanasia campaigner Dr Philip Nitschke is appealing his suspension by the Medical Board of Australia, saying the organisation exceeded its authority.
A five-day hearing began on Monday at the Northern Territory Health Professional Review Tribunal in Darwin.
In July, the board used its emergency powers to immediately suspend Dr Nitschke, after ruling he posed "a serious risk to the health and safety of the public".
The ruling followed the suicide of Perth man Nigel Brayley, 45, who died in May after communicating with Dr Nitschke and attending an Exit International workshop in Perth in February.
Dr Nitschke said the medical board told him his view that people have a right to choose to take their own life was incompatible with his responsibility as a doctor.
The suspension prevents him from practising anywhere in Australia and is an interim measure pending the outcome of an inquiry.
At the time, Dr Nitschke said he did not need a medical certificate to continue his work with Exit International, but would fight the suspension so others could not use it to discredit him and his message.
"To suggest that my passing acquaintance with Brayley implies a doctor-patient relationship, and an implied duty of care, makes a mockery of good medical practice," he said.
Speaking to AAP on Monday before the hearing began, Dr Nitschke said his lawyers would argue that the board exceeded its authority and would question its use of emergency powers.
He said every rational adult had the right to determine what they did with their own body, which may include ending their own lives.
* Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14 or the Suicide Call Back Service 1300 659 467.
