Urging release of the chief justice, Human Rights Watch also appealed to the United States and other governments to push President Pervez Musharraf to promptly take meaningful steps to restore respect for the rule of law in Pakistan.
Terming the detention "illegal," the watchdog asserted that the dismissal and detention of the senior judge contravened provisions for the removal of judges under Pakistan's constitution, and severely undermined judicial independence in the country.
"By brazenly and unlawfully dismissing, detaining and humiliating the chief justice of the Supreme Court, President Musharraf has created a constitutional crisis at the judiciary's expense," said Ali Dayan Hasan, South Asia researcher for Human Rights Watch.
Musharraf, he said, has undermined judicial independence before and nothing could make that more clear than his "arrest" of the Chief Justice.
Chief Justice Iftikhar Muhammad Chaudhry was dismissed by Musharraf on March 9 for "misuse of office."
The government subsequently declared the chief justice to be "non-functional" and held him incommunicado at his official residence.
The Human Rights Watch criticised the Pakistani government for not releasing any details of the charges and its decision for an in camera hearing by Pakistan's Supreme Court of the reference made by it.
The watchdog demanded public hearing, maintaining that Pakistan Bar Associations and other human rights organisations too have asked for open hearing in the interest of a "fair" hearing.
"The Pakistani government must allow Justice Chaudhry a fair, open hearing where he has adequate opportunity to study the charges leveled and benefit from legal advice," said Hasan.
"Anything less will amount to a mockery of justice."
On Monday, lawyers across Pakistan protested the arrest and detention of the chief justice by boycotting court proceedings and holding peaceful demonstrations.
Police in the central Pakistani city of Lahore violently broke up one of the largest demonstrations ever by high court lawyers in Pakistan.
Human Rights Watch said eye witnesses said that protestors were peacefully marching down a main thoroughfare when police used batons to break up the procession.
"The brutal assault on lawyers demonstrating for the chief justice raises bigger issues about the rule of law in Pakistan," said Hasan. "The government needs to respond to this by taking appropriate action against those government officials responsible."
The watchdog said that the move to oust Justice Chaudhry points towards the Pakistani government's determination to ensure control over the judiciary in the run up to elections due by the end of 2007.
Recently, Justice Choudhury has taken up several human rights cases including initiating proceedings in cases involving enforced disappearances, the watchdog noted.
Human Rights Watch said research by it indicates a pattern of "disappearances" in Pakistan involving US complicity in the abduction of individuals in the "global war on terror" and their interrogations by US law enforcement agents in illegal detention centres run by the Pakistani military's Inter Services Intelligence agency.
