“I thought this policy was connected to a Treaty somehow.”
It is most likely one of the rules imposed by America after WW2 and is in their constitution, like not having nuclear weapons or air craft carriers. (They have a huge helicopter carrier which skirts the constitutional barrier.)
However, if they haven’t developed nuclear weapons, especially after they had to officially protest Obama’s policy of removing nuclear weapons from their supposed umbrella, they’re idiots.
I would not be surprised to learn they had developed but not officially deployed a nuclear deterrent. Because of his ultra-idiot nuclear policy Obama will likely go down in history as the greatest nuclear proliferator in history. He proved that any liberal could, without asking, remove the nuclear umbrella and renounce first use; which will likely guarantee a nuclear war.
Japan could have nuclear weapons in the time it takes to assemble nuclear weapons!