Guys, I am not sure we are on the same page!
Are you really serious that these guys need to be dealt with in the same way you would deal with a pickpocket or a common criminal!
They are terrorists and the normal criminal code has no relevance for them. No country has successfully fought a war with the terrorists with the "normal" criminal code and procedure.
So the issue is: Does Pakistan believe that they are terrorists or not? Does the world believe that they are terrorists or not? If they are, the normal process of law becomes meaningless and they have to be dealt with in a separate manner.
I think Asim hit the nail on the head when he said that Pakistan has different priorities. So LET may be a problem for India and the USA but a lower priority for Pakistan.
So the task for India and the USA is to increase the priority for you. To make Pakistan aware that the cost of not doing anything is not negligible. It better be done through diplomatic means like the UN resolutions to make it easier for Pakistan.
The talk of any judicial process is red-herring. What judicial process is followed against enemies of the country, against the Fata rebels, against the separatists?
No question Pakistan has different priorities, and part of the reason she has other priorities is forced on her because of the existing WoT, economic issues etc. I don't think forcing Pakistan to act on this particular issue at this point in time is going to be helpful, not with a relatively weak civilian government already battling several crises. Excessive pressure runs the risk of further destabilizing the country and therefore actually being counterproductive in the long run.
I think Pakistan's priorities right now are the correct ones, though the actions taken against the groups mentioned were unavoidable, and doable. I think there is more that can be done on this front in the medium term, but what I think about that later...
The issue isn't about treating terrorists vs ordinary criminals, its about rule of law. If the Pakistani parliament wants to pass a law such as TADA or POTA or the PATRIOT Act, then I have no issues if the GoP utilizes the provisions in that law for cracking down and punishing terrorists. But it needs to be done according to the law.
Your question about the crackdown in FATA and Baluchistan is a valid one, but it isn't an entirely applicable analogy. Baluchistan is perhaps the closest, since comes under the ambit of the Pakistani constitution, whereas FATA does not.
The biggest difference in Baluchistan is that you have armed groups fighting the State - they are killed in combat or arrested during searches and/or encounters. There really aren't that many questions about the individuals killed during hostilities, since they pose a direct threat to LEA personnel. There have been a lot of questions raised in Pakistan, and a lot of anger, by political parties, civic organizations and the media over the arrests of individuals - precisely because those arrests and detentions have been considered illegal and without proper trials and due process.
In fact one of the efforts by the PPP government has been to assuage the sentiment in Baluchistan by releasing political figures and prisoners that had been detained extra judicially, and curtail the military operations drastically.