The US might suspect, I doubt they actually have any evidence, otherwise Gul and these other retired officers would be in prison in Pakistan.
The effort to get H Gul blacklisted was probably initiated by the Indians because of his support for Kashmiri groups, trying to utilize the leverage they (the Indians) had after the Mumbai attacks, and probably failed because of that reason as well, since no actual connection between Al Qaeda and terrorism such as Mumbai could be established, and Pakistan was not going to let someone be punished for supporting what it considers a legitimate struggle against Indian occupation.
And we are prosecuting those involved. Gul has not condoned the Mumbai attacks - he might be a JuD/LeT supporter in terms of supporting the Kashmir cause, but I have yet to see anything that suggests he knew about the Mumbai plot and supported the planning and execution of the Mumbai attacks in anyway.
I don't share your perspective on the HG issue. HG has not been touched because he has powerful allies that include his patrons in Saudi.
Its a little hard for me to believe that HG being the political patron and advisor to LeT, had no clue about the most vicious attack ever organized by the LeT on Indian soil.
And what did Gul actually say about the Mumbai Attacks? That it was an inside job! Perhaps Mr. Gul is trying to deflect attention from his pets in LeT.
Besides, the LeT is no longer fixated on Kashmir. As the French Investigator Brugiere pointed out, the salafi- inspired LeT has strong linkages with AQ and is now focused on a pan-jihadi agenda that goes way beyond Kashmir.
The US government probably has a very good reason for putting Gul on the terrorist list. If they were being cavalier about it, they would've put 50 ex-officers on the list as opposed to just 5.
Gul, 71, has acknowledged that he once was a member of a group of retired ISI officers, Pakistani scientists and others that was suspected by the United States of giving material support to the Taliban and al-Qaeda. Gul said the organization, Ummah Tameer-e-Nau, was formed by a group of Pakistani businessmen to aid war-ravaged industries in Afghanistan.
The U.S. Treasury Department declared Ummah Tameer-e-Nau a terrorist group after a search of the group's offices in the Afghan capital, Kabul, unearthed documents referencing plans to kidnap a U.S. diplomat and outlining basic physics related to nuclear weapons.
Even Musharraf named Gul in 2006 as one of the retired ISI officers suspected of fomenting unrest in the tribal areas.
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DAWN News
October 2006
ISLAMABAD: Two former chiefs of the Inter-Services Intelligence have rejected as baseless a statement of President Pervez Musharraf about former officials of the agency abetting Taliban.
Former ISI directors-general Asad Durrani and Hameed Gul, talking to Dawn, said there was no need to issue such a speculative statement.
Mr Gul said former officers of the ISI were not involved in helping Taliban. He said the Taliban surfaced in 1994, some five years after his tenure as ISI chief was over and about three years after his retirement from the army.
(Does anyone really believe HG had no role in the jihadi/taliban network after he formally retired??)
He said Gen Musharraf was a distinct type of team captain who was scoring goals against his own team by accusing his own people. The nation was astonished to see the captain hell-bent to see his own team’s defeat, he said.
Mr Gul claimed that a charge-sheet against him was being prepared.
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So you'll have to excuse me if I take the implication that HG does not support LeT/Taliban/AQ in the global jihad context(beyond Kashmir) with a big pinch of salt.