Probably the last on this for a while. Probably.
This entire interview with the Head of the Research Center for Fiq’h Affairs in Iran’s Parliament is worth a read, but this portion really jumped out at me:
Q: One of the questions over the leadership fatwa banning nuclear weapons is if the statement is in fact Taqqiya (minor or benign falsehood in a matter of life and death). They say since Taqqiya is permitted in Shia Fiq’h, Islamic Republic of Iran has issued the statement, contrary to its real intention, only in a bid to defend itself against the enemies and it is possible that Iran violates the fatwa once it gains enough power.
A: Islam approves Taqqiya under some special conditions and has particular limitations. But the issue of weaponry competition is so clear that it is not subject to Taqqiya.
Hence the answer is that: A Taqqiya fatwa is acceptable when the issue, for which a fatwa is issued, is changeable, while the dangers of nuclear weapons will never change. This is a perfect and complete fatwa and not a Taqqiya fatwa. A Taqqiya fatwa is limited and can be changed but when a fatwa is issued in the international arena, the opposite cannot be proved to be right otherwise Shia fiq’h is questioned.
I can’t speak to the accuracy of this, but it’s important to read what the Iranians say about it.