Your first paragraph is beyond dispute IMO. No terrorist group will ever have the resources or expertise to build a nuclear weapon.
I'm more interested in your second - that any nuclear weapon supplied to terrorists by a government could easily be tracked back after it is detonated. I can see there being good circumstantial evidence based on the general type of bomb used (i.e. uranium vs. plutonium) and its yield, but since the bomb is atomized in the explosion, can there be conclusive evidence?
- wolf
Generally you track the fissile material (as that's the unique and most important part). It's called nuclear forensics: http://cstsp.aaas.org/files/Complete.pdf It requires international cooperation and some time, but generally the answer to the question of 'can there be conclusive evidence?' is: yes.
There's been a lot of hand wringing about our declining nuclear forensics capabilities in recent years, but I have zero doubt that if someone were to actually nuke a major country that these resources would be put back into play immediately. This would most likely only apply to uranium bombs anyway, as plutonium bombs are a whole extra step more difficult to make.
