is it possible to completely expunge data in bzr?

[Tom Marble]

All:

An interesting scenario has presented itself in managing
large, complex projects where some source code may need to
be temporarily (or permanently) cloistered (e.g. source
code with differing provenance).

To clarify the use case let's say I accidentally checked
in some nuclear launch codes to the VCS, then realized
my mistake and wanted to remove any trace of them.

Apparently this would be problematic when using VCS's
such as Mercurial [1].  Obviously one cannot "unring the bell"
if the repository has been published publicly.  However
if one realizes that the launch codes have been checked
into bzr (and not the most recent transaction) can they
be expunged?

Regards,

--Tom

[1] I committed a change containing nuclear launch codes, how do I delete it permanently?
http://www.selenic.com/mercurial/wiki/index.cgi/FAQ#head-8315917f7ee72783fff196558bc462d7165b5961