I don't know what your point was, but there are classified patents with well-defined rules.
Basically, patent applications get audited by DoD/CIA/whomever, and if one of them is deemed sensitive to national security, it gets classified and the inventor/assignee is forced into treating it as state secrets. In return, I think they get special consideration as a supplier from the government (which could be a windfall) and a standard patent term which starts immediately after the state secret is relinquished.
There are also rules for what happens if someone independently re-patents the thing that is secretly patented. In short, the re-inventor gets screwed completely, the state secret gets reviewed, and if admissible the original patenter's term kicks in. So, yeah, classified patents exist (or at least they did in the cold war days, dunno about now), and they're buried landmines.