Refers to restrictions of competition by agreements or business prac- tices, which are seen by most jurisdictions as being particularly serious and normally do not produce any beneficial effects. They therefore almost always infringe competition law. Under EU law, the most prominent examples on the horizontal level include agreements between competitors that fix prices, allocate markets or restrict the quantities of goods or services to be produced, bought or supplied. Examples of hard-core restrictions in vertical relationships (that is, between undertakings operating at different levels of the production or distribution chain) are resale price maintenance and certain territorial restrictions. Provisions of an agreement that contain such restrictions are also referred to as black clauses and prevent the agreement from benefiting from a block exemption. Furthermore, agreements containing black clauses can only exceptionally be exempted on the basis of an individual assessment.

Source: Glossary of terms used in EU competition policy, Antitrust and control of concentrations, European Commission, 2002