In the case of nuclear weapons specifically, it actually was a shock when the US tried to enforce the "born secret" doctrine (which said that information about

In the case of nuclear weapons specifically, it actually was a shock when the US tried to enforce the "born secret" doctrine (which said that information about weapon design and mechanics -- even if figured out from nothing but public, non-classified sources -- would automatically become classified as of the moment the person figured it out). See US v. Progressive for the details: https://en.wikipedia.org/wiki/United_States_v._Progressive,_Inc https://en.wikipedia.org/wiki/United_States_v._Progressive,_.... Amusingly, the argument was made -- and made seriously -- that the mere fact that the government had pursued the case was a leak of "born secret" information, since the attempt to suppress the information was tacitly an acknowledgment that it was correct (since incorrect information would not be subject to "born secret").