Article 19: Right to freedom of opinion and expression

Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.

Definitions of the right to freedom of opinion and expression

The right to freedom of opinion and expression is enshrined in 
Article 19 of the Universal Declaration of Human Rights.

The right is enshrined in Articles 19 and 20 of the International Covenant on Civil and Political Rights:

Article 19
1. Everyone shall have the right to hold opinions without interference.
2. 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.
3. The exercise of the rights provided for in paragraph 2 of this article carries with it special duties and responsibilities. It may therefore be subject to certain restrictions, but these shall only be such as are provided by law and are necessary:
(a) For respect of the rights or reputations of others;
(b) For the protection of national security or of public order (ordre public), or of public health or morals.

Article 20 
1. Any propaganda for war shall be prohibited by law.
2. Any advocacy of national, racial or religious hatred that constitutes incitement to discrimination, hostility or violence shall be prohibited by law.

In its General Comments No 10 and 11 of 1983, the Human Rights Committee comments on the freedom of opinion and expression: http://www2.ohchr.org/english/bodies/hrc/comments.htm.

It is contained in Articles 12 and 13 in the Convention on the Rights of the Child:

Article 12
1. States Parties shall assure to the child who is capable of forming his or her own views the right to express those views freely in all matters affecting the child, the views of the child being given due weight in accordance with the age and maturity of the child.
2. For this purpose, the child shall in particular be provided the opportunity to be heard in any judicial and administrative proceedings affecting the child, either directly, or through a representative or an appropriate body, in a manner consistent with the procedural rules of national law.

Article 13
1. The child 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 the child's choice.
2. The exercise of this right may be subject to certain restrictions, but these shall only be such as are provided by law and are necessary:
(a) For respect of the rights or reputations of others; or
(b) For the protection of national security or of public order (ordre public), or of public health or morals.

It is also containd in Article 13 of the International Convention on the Protection of the Rights of All Migrant Workers and Members of Their Families:

1. Migrant workers and members of their families shall have the right to hold opinions without interference.
2. Migrant workers and members of their families 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 their choice.
3. The exercise of the right provided for in paragraph 2 of the present article carries with it special duties and responsibilities. It may therefore be subject to certain restrictions, but these shall only be such as are provided by law and are necessary:
(a) For respect of the rights or reputation of others;
(b) For the protection of the national security of the States concerned or of public order (ordre public) or of public health or morals;
(c) For the purpose of preventing any propaganda for war;
(d) For the purpose of preventing any advocacy of national, racial or religious hatred that constitutes incitement to discrimination, hostility or violence.

The Convention on the Rights of Persons with Disabilities contains this right in Article 21:

States Parties shall take all appropriate measures to ensure that persons with disabilities can exercise the right to freedom of expression and opinion, including the freedom to seek, receive and impart information and ideas on an equal basis with others and through all forms of communication of their choice, as defined in article 2 of the present Convention, including by: 
(a) Providing information intended for the general public to persons with disabilities in accessible formats and technologies appropriate to different kinds of disabilities in a timely manner and without additional cost; 
(b) Accepting and facilitating the use of sign languages, Braille, augmentative and alternative communication, and all other accessible means, modes and formats of communication of their choice by persons with disabilities in official interactions; 
(c) Urging private entities that provide services to the general public, including through the Internet, to provide information and services in accessible and usable formats for persons with disabilities; 
(d) Encouraging the mass media, including providers of information through the Internet, to make their services accessible to persons with disabilities; 
(e) Recognizing and promoting the use of sign languages. 

The right is also contained in Article 9 of the African Charter on Human and Peoples' Rights:

1. Every individual shall have the right to receive information.
2. Every individual shall have the right to express and disseminate his opinions within the law.