I should have chosen my words more carefully, but the blobs with ads will have some sort of DRM on them, which is technically illegal to decrypt and cut out.
> Removing DRM on something you own for personal use is perfectly legal.
Perhaps some places. In the US, it is perfectly legal to "violate" copyright restrictions for purposes like fair use. But if the data is protected by any kind of security, it is a felony to bypass that security (even for fully legal purposes).[1]