The general principle of removing DRM is forbidden, at least in the US, which is presumably why DRM removal tools are distributed through the same shady web sources as pirated content.
"No person shall circumvent a technological measure that effectively controls access to a work protected under this title."
The ambiguity is resolved by the explicit definition provided in the section: 'a technological measure "effectively controls access to a work" if the measure, in the ordinary course of its operation, requires the application of information, or a process or a treatment, with the authority of the copyright owner, to gain access to the work.' So the word 'effectively' isn't very effective here.
"No person shall circumvent a technological measure that effectively controls access to a work protected under this title."
https://www.law.cornell.edu/uscode/text/17/1201