Pakistan's Supreme Court has begun hearing a petition by former PM Nawaz Sharif who wants the right to return to the country and contest elections.
Mr Sharif was deposed in a coup
Mr Sharif, who was deposed by President Pervez Musharraf in a coup, says he and his brother, Shahbaz Sharif, are being prevented from returning to Pakistan.
This is despite a 2004 Supreme Court order allowing them to come back.
Nawaz Sharif, his brother Shahbaz Sharif and former PM Benazir Bhutto are all living in exile abroad.
Gen Musharraf ousted Mr Sharif in 1999, seizing power in a military coup.
Observers say the government is determined to keep the Sharif brothers, as well as Ms Bhutto, away from the country until after the parliamentary elections.
Mr Sharif denies having done a deal with the government to stay away for 10 years.
Chief Justice Chaudhry has had a long run-in with Gen Musharraf
But the government's senior lawyer said Mr Sharif had agreed to the arrangement, and that he had documents he was prepared to show the court to prove it.
The application was heard by the Chief Justice, Iftikhar Muhammed Chaudhry, whom the Supreme Court reinstated last month after his suspension by President Musharraf.
The court will meet again next week.
Gen Musharraf said earlier this week that return of exiled leaders could lead to anarchy in the country.
In 1999 a special anti-terrorism court convicted Mr Sharif on charges of hijacking and terrorism and passed a sentence of life imprisonment.
The ousted premier was charged with endangering the lives of the country's current military ruler, Gen Musharraf, and nearly 200 passengers on a commercial flight.
Gen Musharraf was returning to Pakistan from Sri Lanka and Mr Sharif was said to have issued orders preventing his plane from landing in Karachi.
The plane was eventually able to land and Mr Sharif was overthrown after the military seized control.
In the same year Ms Bhutto and her husband were convicted of corruption and also given jail sentences.
The question of whether Mr Sharif and Ms Bhutto can be disqualified from contesting the election under a law blocking convicts from doing so is, according to observers, an open question.