> What you seem to be missing is that it's very far from certain that the original claim was actually a valid use of the DMCA.
It seems pretty valid, for the following reasons:
1) Authors who post youtube videos never gave youtube permission to publish the material outside of youtube
2) RIAA is clearly a youtube author who satisfy point (1).
3) youtube-dl is at the edge of youtube - it clearly pulls data from inside youtube to outside of youtube
4) RIAA cannot go directly against youtube-dl on the grounds of copyright infringement, because youtube-dl never published the material, their users did.
5) But youtube-dl enables end users to violate RIAA's copyright, so RIAA might still have valid claim
6) RIAA just needed to find alternative legal mechanism to shut down youtube-dl, and that seems to be the
"circumvention of technological protection mechanism"
7) This circumvention is obvious after you see (3).
8) Possibly there's the fact that youtube has promised RIAA and their member companies that their youtube system
does not allow downloading published video material, and their TOS enforces it
9) Thus from (1),(2),(3),(4),(5),(6),(7) and (8), you can see that the DMCA notice is valid use of DMCA.