The Act has been criticised by civil rights activists who see it as a barrier to free speech. But this week's new exemptions appear to have done little to reduce their concerns.
In terms of the DMCA, the Library of Congress, of which the US Copyright Office forms part, is required to review the operation of the Act every three years in order to assess whether the systems being used to control access to copyrighted works are affecting the legal use of those works.
Where such use is suffering then the Librarian of Congress is empowered to grant exemptions from liability under the Act.
The new exemptions are, according to a statement issued by the Librarian of Congress:
Compilations consisting of lists of internet addresses blocked by commercially marketed filtering software applications that are intended to prevent access to domains, web sites or portions of web sites, but not anti-spam lists.
Computer programs protected by 'dongles' that prevent access due to malfunction or damage and which are obsolete. (A dongle is a mechanism to ensure that only an authorised person can use or copy a program. A popular type of dongle is a hardware key that plugs into a computer's USB port, which a program will refer to for verification.)
Computer programs and video games distributed in formats that have become obsolete and which require the original media or hardware as a condition of access.
Literary works distributed in e-book format when all existing e-book editions of the work (including digital text editions made available by authorized entities) contain access controls that prevent the enabling of the e-book's read-aloud function and that prevent the enabling of screen readers to render the text into a specialised format.
Activist group the Electronic Frontier Foundation (EFF) expressed disappointment that the ruling did not go further.
"Consumers are the real losers in today's ruling, because the Librarian of Congress is ignoring the rights of nearly everyone who has purchased CDs and DVDs," said EFF Staff Attorney Gwen Hinze.
"We're disappointed that the Copyright Office and the Librarian of Congress did not recognize the significant impact that the DMCA is having on millions of consumers' ability to make reasonable uses of digital media they've purchased."