The anti-copyright law says you can't reverse engineer anything which is used for copyright protection. This is how they went after the programmers who were making software to allow them to view DVDs on Linux. You would think that you could buy a product and use it as you like. Not so.
There is no way you could be hit for this though. Too easy to do.
However, suppose that instead of using a magic marker one had to use special software to decode the protected disks. They would probably go after the people who made the software and distributed it. The software doesn't have to be hard to make. It just has to be covered by the anticopyright law.
Fair use says that you can make limited copies for yourself (and a few other purposes). It doesn't say that the content providers have to make it easy for you to copy their stuff.