I would be looking for their processing/reprocessing capability, ie to convert yellowcake to uranium hexafluoride and enrich it to weapons grade U235 content.
Canada and Japan both also have that capability, but have never made a weapon, and lack the requisite corruption to get away with covert processing.
-Let's not get into the US contractor that "lost" over 100kg of HEU, coincidentally at the same time Israel became a nuclear power (US contractor was run by people of the Jewish faith, coincidentally)