More than five years since the terrorist attacks on the United States in September 2001, global responses to terrorism have contributed to an array of threats to freedom of expression and the danger is "real, catastrophic, accelerating," writes Human Rights Watch.

"Counterterrorism has given new vigour to some old forms of censorship, and created new ones," writes essay author Dinah PoKempner. Since 9/11, a growing number of governments have introduced laws criminalising the glorification of terrorism. In 2004, only three European countries had such laws. By mid-November 2006, 36 countries had signed the Council of Europe Convention on Terrorism, which requires states to criminalise "provocation" of terrorism, a crime that could include indirect incitement.

The United Kingdom and Denmark have recently adopted laws on promotion or glorification of terrorist acts. In Turkey, a terrorism law was amended in 2006 so that speech characterised as "propaganda" for terrorism was punishable. In Russia, a similar law was amended to punish speech that supports "extremism," notes PoKempner. Meanwhile, hate speech is increasingly becoming the rationale for imposing criminal or administrative sanctions against those thought to be extremists.