If a federal prosecutor believes there is a criminal case to be made against George Bush, Dick Cheney, George Tenant, or whomever, then he or she should attempt to obtain the appropriate indictment.
We should have a national debate (with some teeth in it) on this topic and bringing charges against a former president will surely launch such a debate.
You realize, of course, that President Obama has reserved the right to authorize enhanced interrogation techniques (excluding, I believe, waterboarding), and since you apparently believe that torture was practiced in Abu Ghraib, I am assuming that if our current president ever authorizes enhanced interrogation techniques that you believe that he too should be prosecuted for authorizing torture and that you will not waffle because of concern for innocent lives or national security.
I also assume every week that I will win the lottery.
It isn't going to happen though because Barrack Obama is now the President and he realizes that to allow such a prosecution to take place will open the door for him to be prosecuted should he cross a gray line.
Presumably someone (on this thread) has or can offer a "legal" justification for other countries prosecuting an American official for alleged crimes that are neither committed on the soil of that country nor against its citizens, but it is utter nonsense.
I might find the idea a bit more acceptable if I saw these countries who fashion themselves champions of international law attempting to prosecute
Fidel Castro, Vladimir Putin, Hu Jintao, Kim Jong Il, Ali Khameni, Basshar Al-Assad, or Robert Mugabe (to name but a few).
Only an muddy headed partisan will think that it is appropriate to allow someone like Baltasar Garzon to prosecute American officials for alleged crimes that did not take place in his country or against his fellow citizens.
If it is really necessary to explain why this is a horrible idea (no matter what your political persuasion may be) then the mud has, apparently, solidified.