A fascinating e-mail: “When I was in the Air Force I was a member of the Air Intelligence Agency. Specifically, I was a Signals Intelligence Analyst. Our collection efforts were governed by directives – the United States

Signals Intelligence Directives (USSID) published by the National

Security Agency. One of our most important USSIDs was USSID 18, an old

version of which can be found here.

“In a nutshell USSID 18 protects our Fourth Amendment rights and forbids

collection efforts against US citizens except under extraordinary

circumstances, circumstances I never came across in 10 years of service.<br.

“In the event of inadvertent collection, transcripts are immediately

destroyed, tapes are degaussed, and a report detailing the incident and

what efforts are being implemented to ensure it doesn’t happen again

gets sent to NSA. It was a very sensitive issue.

“It’s entirely possible that Able Danger violated similar rules and, once

an oversight agency discovered that, the project was shut down. That

theory could also help explain the zealotry with which Able Danger

material was destroyed. No, it wouldn’t matter that the information was

garnered from open sources.”