Everyone has the right to freedom of expression. In the UN system, this is provided by Article 19 of the International Covenant on Civil and Political Rights (ICCPR). This right can be limited though, where that is necessary to protect the rights of others.
So, for instance, a person’s freedom of expression can be restricted by the State if they incite hate or violence against another person or group. In fact the ICCPR expressly requires that “advocacy of national, racial or religious hatred that constitutes incitement to discrimination, hostility or violence … be prohibited by law” (Article 20(2)).
So freedom of expression can be restricted where the rights of other people will be affected.
However, under international human rights law, no one has the right not to be offended or “outraged”. Causing offence by itself is not a justification for a state’s restricting anyone’s freedom of expression, and certainly not for making such expression a crime.
The UN Human Rights Committee, which oversees the ICCPR, specifically says: “Prohibitions of displays of lack of respect for a religion or other belief system, including blasphemy laws, are incompatible with the Covenant” (General Comment No 34). In 2014, this Committee expressed concern at Ireland’s blasphemy law (in its ‘Concluding Observations’ on the state’s implementation of the ICCPR).