A commission investigating the May U.S. raid that killed the al Qaeda chief has ordered the Pakistani government to keep them detained.
Pakistani authorities recently indicated they were about to allow bin Laden's youngest wife to go to her native country of Yemen.
The commission's order, which was issued late Tuesday and is supposed to be binding, was directed in part at Pakistan's powerful Inter-Services Intelligence spy agency, which tends to operate beyond civilian control and is believed to be holding the family.
It was not clear if the powerful security agency would heed the order.
Pakistani commissions and inquiries into other issues in the past have accomplished little or seen their findings never published.
The ability of the U.S. to carry out the operation unilaterally infuriated Pakistanis who saw it as a violation of their country's sovereignty. At the same time, U.S. lawmakers were outraged to learn that bin Laden had managed to hide, apparently for years, in a city that is home to a top Pakistani military academy.
Bin Laden's discovery has raised suspicions that Pakistani's armed forces or intelligence services aided bin Laden, but U.S. officials have said they've seen no evidence that Pakistan's top civilian or military leaders knew of his whereabouts.
At first, it appeared the government was willing to let the army handle the inquiry into the bin Laden raid on its own. But opposition leaders and others demanded an independent commission that included nonmilitary representatives, and the government eventually agreed.
The commission is charged with investigating how bin Laden managed to hide in Pakistan for so long, and the circumstances surrounding the U.S. operation.
According to a statement late Tuesday, the group promised a thorough and independent investigation. It said it would call upon senior civilian and military leaders to attend proceedings if necessary, and encouraged members of the public who had information to contact it.
The Associated Press contributed to this story