This is everything to do with the DMCA. YouTube claims it is required by law to take down content that receives a takedown notice. That law is the DMCA. Edit: I'm probably wrong. It seems a claimant can also issue a block. They do not have to issue a takedown notice. That seems to be the problem right there!!

(However) I find it really difficult to believe the claimant in this case has no control over what YouTube does, as they have previously claimed. It may have been Content ID that got the identification wrong, but the claimant should not issue a block if it is a false claim.

Anyhow, Rousseau found a way around it by uploading a new version that received a copyright claim from a different company, instead of a block. He'll still have to go through the dispute process, at least we can watch the video because YouTube is not obliged to (and does not) take down the video.