I think this is every bit as against the law as just using DRM breaking software. It’s circumventing digital rights management. If you get picky, it’s using digital means to do so.
I think using DMCA to prevent the person who bought the property to use it in a way consistent with the terms of sale (IE “to read it” versus “to give away 1000 copies” or “to plagiarize it” is an immoral piece of legal action, but given that DMCA exists, I don’t believe that this is any less infringing than any other method.
