I'm still looking, but found this one that I think is the origin of the idea

Several hours later....

Spending a substantial part of my day reading the Library of Congress Copyright office's "Exemption to Prohibition on Circumvention of Copyright Protection Systems for Access Control Technologies", I can confirm that I was wrong about the legality of circumventing copyright protections on DVD's and BlueRay discs for the purposes of space-shifting (to store and view media in a different format or location). Here's the relevant section of the decision:

Proposed Class 6: Audiovisual Works—Space-Shifting Proposed Class 6 would allow circumvention of TPMs protecting motion pictures and other audiovisual works to engage in space-shifting. Petitioner failed to provide legal arguments or evidence to demonstrate that space-shifting is a noninfringing use. Additionally, petitioner did not participate in the public hearings to support its petition or clarify whether the proposed exemption would extend to commercial services. Opponents argued that petitioner did not provide the evidence necessary to support an exemption, citing several substantive and procedural deficiencies. NTIA recommended denying the proposed exemption. As discussed more fully in the Register’s Recommendation, the Register does not recommend the adoption of an exemption for proposed Class 6.

D. Conclusion Having considered the evidence in the record, the contentions of the commenting parties, and the statutory objectives, the Register of Copyrights has recommended that the Librarian of Congress publish certain classes of works, as designated above, so that the prohibition against circumvention of technological measures that effectively control access to copyrighted works shall not apply for the next three years to persons who engage in noninfringing uses of those particular classes of works.

Not that you asked, but my personal opinion on the matter is this should be considered an exemption. That the petition was denied because the petitioning party didn't show up to the hearing is quite frustrating, but doesn't change the fair-use nature of space-shifting media for personal viewing. If it were me, I would have pointed out that there are no digital alternatives to space-shifting legally obtained UHD 4K BlueRay discs, especially for offline viewing and for viewing at the same high quality.

Frankly, I think DMCA is a load of bullshit and should absolutely be abolished in entirety, but if nothing else, there needs to be a strong petitioner actually attending the meetings to allow for broader fair-use exceptions to be heard. On the bright side, i learned a lot about exceptions to DRM circumvention i didn't already know about, namely that it's legal to alter software on phones, tablets, pcs, and even cars and land-vehicles for purposes not otherwise prohibited, including smart home devices and CARS. Fuck yea. Imma break all kinds of shit on my google homes.