Cass County Music is connected with just about all of Don's catalog, so pretty much whatever he wrote or co-wrote would fall under their purview.
However, with YouTube, it's guilty until proven innocent. Cass County Music could tell YouTube to take down a video you've posted that does not actually contain material copyrighted to Don - for instance, a solo video of Glenn, Tim, Joe, Randy, Bernie, or Felder - and it would go down without question. You would have to issue an appeal to get it put back, and to do that you would have to be able to provide proof of copyright. Since you can't do that, your video stays down (and, on the third instance, your account disabled) regardless of whether or not Cass County Music has any legal claim.
I know this because it's happened to me under some of my many YouTube IDs. I used to post videos to YouTube like a maniac (one of which was the video of "How Long" that inspired them to re-record the song but ANYWAY...). I've honestly lost track of how many IDs I made up - one would get shut down, I'd create a new one. On one account, I had posted live videos of Glenn doing Desperado and also Glenn doing the Heat Is On, and Cass County Music told YouTube to remove both.
In fact, the first video I ever got taken down was a video of Joe photos set to the Stevie Nicks song, "Has Anyone Ever Written Anything for You." Paterno et al, representing Joe, demanded the video taken down. Joe had no copyright on those photos and the song was copyrighted to Stevie Nicks and Welsh Witch Music, but that made no difference - YouTube did as Paterno asked regardless.
Why did I upload those videos? It was because I wanted to share the videos I didn't have room for on my sites - plus, in the beginning, I only had a Glenn site so all the songs by the other guys weren't getting put up. It felt like such a waste that no one could see them. (Back then there wasn't much Eagles stuff on YouTube.)
I don't have the time to do that kind of thing anymore, so my crazy YouTube days are over. However, I really don't need to upload anything anymore... thanks to the increasing commonality of torrent sites who provide access to rarities, the increasing ease of ripping videos to file format, and the increasing speed of internet connections which enables more convenient uploading/downloading, the videos are circulating much more widely. Thus, I can just leave it to other people to post them.
That's why CCM's "crack down" is a big waste of effort - the videos are still out there. The barn door's lock is broken and slamming that door shut only lasts until the next cow nudges it open again.