Isn't violating copyright(except for fair use) already illegal? If you photocopy a book fully and give it your friend, you're already violating copyright and can receive a takedown notice[1], regardless of the anti-decryption clause of the DMCA.
IIRC/IANAL, violating the copyright without commercial intent (you are not selling it) is still a civil law violation although DMCA takedown provisions still apply. Breaking DRM elevates it to a criminal charge.
I think that is the case, but correct me if I am wrong, it has been awhile since I studied this.
If only there was some constitutional amendment that promised people the right "to be secure in their persons, houses, papers, and effects, against unreasonable searches".
This means: if you have some circumvention device whose presence cannot be detected from outside your home: too bad for the government. They can't do anything about it.
[1] A different provision of the DMCA