"The judge ordered the government that while appeals by their families are pending in the court, the detainees must not be handed over to a foreign agency or to another state," lawyer Shah Khawar told AFP.
Judge Anwar ul Haq of the Lahore High Court is hearing appeals against the detention of nine scientists and administrators associated with the A.Q. Khan Research Laboratories, Pakistan's key uranium enrichment facility.
A total of 13 KRL acting and former employees, including its founder A.Q. Khan -- the father of Pakistan's nuclear bomb -- have been questioned since December over allegations they sold nuclear secrets to Iran and Libya. Three have since been cleared and released. Khan was never detained.
The probe was triggered by a letter to the Pakistani government from the UN's nuclear watchdog, the International Atomic Energy Agency in November.
Pakistan then sent teams of investigators to IAEA headquarters in Vienna, Iran and Libya in December to examine the allegations.
Representing the government in Friday's hearing, deputy federal attorney Chaudhry Mohammad Tariq asked for more time to gather information about the detained scientists.
Tariq told the court he was unable to determine where the nine scientists still under interrogation were being held, despite contacting a range of government departments and intelligence agencies.
The court also directed authorities to inform the families of the well-being of the detained scientists, said Khawar, who represents the family of KRL director general Nazir Ahmed.
Friday's hearing coincided with nationwide protests by lawyers and Islamists who criticized the government for arresting "national heroes."
"We will make an example of those taking steps against our nuclear scientists," parliamentary leader of six-party Islamist alliance Muttahida Majlis-e-Amal Liaqat Baloch told a gathering of some 200 outside Islamabad's Red Mosque after Friday prayer congregation.
The sons of three nuclear scientists and officials detained by government for "debriefing sessions" in alleged leaks of nuclear information to Iran and Libya also attended the protest.
The protestors chanted anti-American slogans calling for a jihad and held posters which read: "FBI get out of Pakistan" and "Immediately release the nuclear scientists."
"The entire nation hates (President Pervez) Musharraf because of his attempts to roll back Pakistan's nuclear programme," Baloch said.
"In a secret deal with (the) US, the Musharraf government has put our nuclear capability on roll back path," Baloch said.