The Invention Secrecy Act 1951 requires the US government to impose secrecy orders on certain patent applications that contain sensitive information, thereby restricting disclosure of the invention and withholding the grant of a patent. Remarkably, this requirement can be imposed even when the application is generated and entirely owned by a private individual or company.
There are several types of secrecy order which range in severity from simple prohibitions on export (but allowing other disclosure for legitimate business purposes) up to classification, requiring secure storage of the application and prohibition of all disclosure.
At the end of fiscal year 2004, there were 4,885 secrecy orders in effect.
The IPKat notes that equivalent provisions exist under the United Kingdom's Patents Act 1977, but that many other countries seem to manage quite well without them. Is it dangerous or irresponsible to publish specifications in some countries but not in others, he ponders. But Merpel asks, isn't a secret patent a contradiction in terms?Best-kept secret here
Worst-kept secret here
Military secrets here