Yes kind of. The "born secret" doctrine says all knowledge related to the creation of nuclear weapons, ranging from nuclear fusion to the production of fissile material, as “born classified".
The doctrine has never been tested in court as no case involving it has gone to trail.
I've definitely figured some things out about nuclear weapons and proliferation that I've never told anyone because of that doctrine. I met a real nuclear engineer at a conference and had dinner and he told me about how he was concerned that people would nick Np237 from a fuel reprocessing system to make nuclear weapons and I pointed out that it was OK to talk about that because I'd seen it in the literature.
The doctrine has never been tested in court as no case involving it has gone to trail.
https://en.wikipedia.org/wiki/Born_secret