People have the right to seek, obtain, receive and hold information about human rights and human rights violations. States should ensure that people are able to peacefully protest, publicize and circulate information and criticize the failure of governments to protect or promote human rights. 

International Standards
Articles 6 and 8 of
UN Declaration on Human Rights Defenders
Article 19 of
Universal Declaration of Human Rights
Article 19 of
International Covenant on Civil and Political Rights

Regional Standards
Article 13 of
American Convention on Human Rights
Article 9 of
American Declaration on the Rights and Duties of Man
Inter-American Declaration on principles of freedom of expression
Article 32 of
Arab Charter on Human Rights (2004)
Article 9 of
The African Charter on Human and Peoples' Rights
Declaration of principles on freedom of expression in Africa
Article 10 in
European Convention for the Protection of Human Rights 

States use different methods to restrict the freedom of speech and expression. Apart from prior restraint and censorship, this can be:

• Strict defamation laws (to protect powerful people from scrutiny)
• Broad and vague restrictions against advocacy (such as the Russian law on extremist activity (2003))
• The criminalization of dissent
  

For a more elaborate overview on restrictions of freedom of speech and expression, please visit the Defending Civil Society Project of the World Movement for Democracy).