It's time to repeal some laws, send in Delta Force, off the guy, leave no evidence, and claim complete ignorance.
Who knows - a little US mission might one day enable Iran to have a litte nuclear mishap with their new toy. Wouldn't that be a shame. If they got their design from the Russians - that would be explanation enough. One day the remains of Chernobyl reactor #4 might be a safer place to be than Iran.