Regular audio CDs don’t have any DRM. (Unless it’s a data CD filled with audio files that have DRM or some such. But regular standard audio CDs that work in any CD player, there’s no DRM. The standard just doesn’t allow for any DRM.) And so the DMCA’s anticircumvention provisions wouldn’t apply to CDs.

But as for the Sony case you’re referencing, I’m not familiar with it, so I’ll have to do more research on that.