Formerly know as the assent procedure, it was introduced by the 1986 Single European Act. It requires the Council to obtain the European Parliament's assent before certain important decisions are taken. The assent principle is based on a single reading. Parliament may accept or reject a proposal but cannot amend it. If Parliament does not give its assent, the act in question cannot be adopted.
As a non-legislative procedure, it usually applies to the ratification of certain agreements negotiated by the European Union, or is applicable most notably in the cases of serious breach of fundamental rights under Article 7 Treaty on European Union (TEU) or for the accession of new EU members or arrangements for the withdrawal from the EU.
As a legislative procedure, it is to be used also when new legislation on combating discrimination is being adopted and it now gives the European Parliament a veto also when the subsidiary general legal basis is applied in line with Article 352 TFEU.