> In addition to the safe harbors and exemptions the statute explicitly provides, 17 U.S.C. 1201(a)(1) requires that the Librarian of Congress issue exemptions from the prohibition against circumvention of access-control technology. Exemptions are granted when it is shown that access-control technology has had a substantial adverse effect on the ability of people to make non-infringing uses of copyrighted works.
> The exemption rules are revised every three years. Exemption proposals are submitted by the public to the Registrar of Copyrights, and after a process of hearings and public comments, the final rule is recommended by the Registrar and issued by the Librarian. Exemptions expire after three years and must be resubmitted for the next rulemaking cycle. Consequently, the exemptions issued in the prior rulemakings, in 2000, 2003 and 2006 are no longer valid.
For a more authoritative and detailed source, the Copyright Office's rulemaking statement begins with several pages explaining its authority and process: http://www.copyright.gov/fedreg/2012/2012-26308_PI.pdf
Next we'll be following orders issued by the Janitor General, I guess.