Discrimination is a human rights violation prohibited by a range of binding human rights standards. The UN Human Rights Committee – the body of independent experts which monitors the implementation of the International Covenant on Civil and Political Rights – has defined discrimination as:

“any distinction, exclusion, restriction or preference which is based on any ground such as race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status, and which has the purpose or effect of nullifying or impairing the recognition, enjoyment or exercise by all persons, on an equal footing, of all rights and freedoms” General Comment N.18: Non-discrimination, Thirty-seventh session (1989), Para 7.

Under international law, discrimination has three distinct elements. There must be: unfavourable treatment; based on a prohibited ground; lacking reasonable and objective justification.

The unfavourable treatment must affect the enjoyment of a right by an individual or group of individuals. In practice, discrimination can occur in a variety of different ways:

• A distinction – for instance the targeting of young black men for police checks;
• An exclusion – for instance refusing identity documents to Roma and Travelers;
• A restriction – for instance limiting the freedom of assembly of lesbian, gay, bisexual or transgender people;
• A preference – for instance favouring applications for public housing from white individuals;
• A segregation – for instance systematically sending Romani children to separate schools without regard for their abilities and needs;
• A denial of reasonable accommodation – for instance, failing to provide wheelchair access to public buildings.

In order for it to be discriminatory, the unfavourable treatment must be based on a prohibited ground such as: ethnicity, religion, national or social origin, language, physical appearance, descent, gender, gender identity, sexual orientation, age or disability.

For there to be discrimination, the unfavourable treatment based on a prohibited ground must lack an objective and reasonable justification. In other words, if the unfavourable treatment pursues a legitimate aim (such as protecting public health or security) and is proportionate to that aim, there is no discrimination. This is generally the most controversial aspect of the determination of discrimination. In many cases, even if the unfavourable treatment pursues a legitimate aim, if there are alternative means for achieving the aim that do not have a negative impact on particular groups, then the unfavourable treatment will be found to be disproportionate thus discriminatory.

Discrimination can be either direct or indirect.

Direct discrimination is unfavorable treatment that is, on its face, based on a prohibited ground. Direct discrimination may be “open”, that is, explicit in the text of a law or clear from a particular practice. It can also be “hidden” but nevertheless identifiable. Examples of direct discrimination include:

• A restriction on access to emergency health care based on residency status.
• A sign outside a restaurant pool reading: “no Roma allowed”.
• The refusal by police to provide protection to LGBT activists during public gatherings.
• A system of public sanitation which systematically fails to cover areas where members of certain minority groups are resident.

Indirect discrimination occurs when an apparently neutral law, rule, procedure or practice results in a disproportionate disadvantage for, or disparate impact on, a particular group which has no objective or reasonable justification. It is the effect of a standard or practice upon a particular group, and not necessarily the intention, that matters in determining whether this type of discrimination has occurred. Examples of indirect discrimination include:

• A law that limits the definition of “housing” for the purpose of social assistance to fixed housing, thereby excluding Roma and Travellers living in caravans.
• A testing procedure used to determine whether children are to be streamed into the ordinary school system or schools for those with learning difficulties that assumes a linguistic ability that children belonging to certain minority groups do not possess.