Air Quality Directive (AQD)

There may be differences between European Commission and a Member State as to what it means that the exceedance period shall be kept "as short as possible". Bearing in mind the Member State's discretion in selecting the measures in a plan, European Commission cannot modify the plan itself, but must convince the Member State to do so, ultimately by starting infringement procedures under Article 258 of the Treaty on the Functioning of the European Union (TFEU), which may ultimately end before the Court of Justice of the European Union (further in the text – CJEU).

The Commission may claim that the Member State has not elaborated an air quality plan as required by Article 23 of the Directive 2008/50/EC. It will be more difficult for the Commission to claim that the measures foreseen therein do not allow the Member State to keep the period of exceedance as short as possible. European Commission would then need to show that the measures taken are insufficient to bring air pollution down (such as because a major source is not addressed at all). As with all infringement cases, European Commission bears the burden of proof for the existence and the extent of an infringement by the Member State.