A while back, a CIA report argued that “it seems unlikely that or any major power can prevent the emergence of more nuclear explosives states because”:

–the requisite materials and technology are already too widely available for technical safeguards and international regulations to be effective.

–competition among the nuclear supplier states guarantees threshold states that diverting and diversifying power programs into explosives programs will not deny them a source of nuclear materials or technology.

–legal restraints on proliferation have lost much of their effectiveness because of the growing political confrontation between industrialized and less developed countries.

–political pressures against proliferation only tend to confirm the view that the nuclear-haves are trying to deny all other countries a valuable prize.

That was written almost 38 years ago in a December 1975 CIA Research Study titled Managing Nuclear Proliferation: The Politics of Limited Choice. The National Security Archives folks published this a while back, but I happened to notice this part of it.