Freedom of speech is the political right to communicate one's ideas via speech. The term freedom of expression is sometimes used synonymously, but includes any act of seeking, receiving and imparting information or ideas, regardless of the medium used. In practice, the right to freedom of speech is not absolute in any country and the right is commonly subject to limitations, as with libel, slander, obscenity and incitement to commit a crime.
The right to freedom of expression is recognized as a human right under Article 19 of the Universal Declaration of Human Rights and recognized in international human rights law in the International Covenant on Civil and Political Rights (ICCPR). Article 19 of the ICCPR states that "[e]veryone shall have the right to hold opinions without interference" and "everyone shall have the right to freedom of expression; this right shall include freedom to seek, receive and impart information and ideas of all kinds, regardless of frontiers, either orally, in writing or in print, in the form of art, or through any other media of his choice". Article 19 goes on to say that the exercise of these rights carries "special duties and responsibilities" and may "therefore be subject to certain restrictions" when necessary "[f]or respect of the rights or reputation of others" or "[f]or the protection of national security or of public order (order public), or of public health or morals".
The AACS encryption key controversy, also known as the AACS cryptographic key controversy, arose in April 2007 when the Motion Picture Association of America and the Advanced Access Content System Licensing Administrator, LLC (AACS LA) began issuing demand letters to websites publishing a 128-bit number, represented in hexadecimal as 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 (commonly referred to as 09 F9), which is one of the cryptographickeys for HD DVDs and Blu-ray Discs. The letters demanded the immediate removal of the key and any links to it, citing the anti-circumvention provisions of the U.S. Digital Millennium Copyright Act (DMCA). In response to widespread internet postings of the key, the AACS LA issued various press statements, praising those websites that complied with their requests as acting in a "responsible manner", warning that "legal and technical tools" were adapting to the situation. The controversy was further escalated in early May 2007, when aggregate news site Digg received a DMCA cease and desist notice and then removed numerous articles on the matter and banned users reposting the information. This sparked what some describe as a digital revolt, or "cyber-riot", in which users posted and spread the key throughout the internet en masse. The AACS LA described this situation as an "interesting new twist".
Banned books are books to which free access is not permitted. The practice of banning books is a form of censorship, and often has political, religious or moral motivations. Bans on books can be enacted at the national or subnational level, and can carry legal penalties for their infraction. Books may also be challenged at a local, community level. As a result, books can be removed from schools or libraries, although these bans do not extend outside of that area. Similarly, religions may issue lists of banned books – a historical example being the Roman Catholic Church's Index Librorum Prohibitorum – which do not always carry legal force.