About a decade ago, David Touretsky (the professor behind this) hosted a "gallery" of versions for the DeCSS decryption software.
"Note to Sony lawyers: no doubt you're eager to rack up another billable hour by sending legal threats to me and my university. Before you go down that unhappy road, check out what happened the last time a large corporation tried to stop the mirroring of technical information here: The Gallery of CSS Descramblers (http://www.cs.cmu.edu/~dst/DeCSS/Gallery). Have you learned anything in ten years?"
http://www.cs.cmu.edu/~dst/Secrets/
I believe CMU's lawyers are well-acquainted with responding to legal threats against him.
This was not a spur of the moment thing - these guys did their homework.
"Ding"
I doubt that. Academics are used to operating with autonomy, and by nature don't confer with lawyers before speaking. So I'm curious why you're so certain he presented this to the lawyers first.
The administration is very cautious and conservative most of the time, and if they had been involved, this would have,at the very least, taken weeks to happen.
That said, the CS department head may have given him a thumbs up (probably even literally), knowing that legal will be forced to back them up, if he asked anyone at all before hand.