When is an environmental assessment required?
The plans and programmes covered by the Directive are those which are: (a) subject to preparation and/or adoption by an authority at national, regional, or local level, or which are prepared by an authority for adoption, through a legislative procedure by parliament or government; and (b) required by legislative, regulatory, or administrative provisions (Art 2).
It is not necessary, for a plan or programme to be ‘required’, that its adoption is compulsory. It suffices that the plan’s or programme’s adoption is regulated by national legislative or regulatory provisions, which determine the competent authorities for adopting them and the procedure for preparing them.32
The Directive’s requirements may either be integrated into existing procedures in Member States for the adoption of plans and programmes or be incorporated into procedures established to comply with the Directive (Art 4).
At the core of the Directive is the requirement to carry out an environmental assessment (EA) for plans and programmes which are likely to have significant environmental effects. An EA includes the preparation of an environmental report, the carrying out of consultations, the taking into account of the environmental report and the results of the consultations in decision-making, and the provision of information on the decision. The EA shall be carried out during the preparation of a plan or programme and before its adoption or submission to the legislative procedure. The Court of Justice has established that a procedure for the total or partial repeal of a plan may also require an EA.33
In some cases an obligation to carry out an EA follows directly from the Directive; in other cases it is for the Member States to determine the likely impact of the plan or programme. An EA must be carried out for all plans and programmes which are prepared for agriculture, forestry, fisheries, energy, industry, transport, waste management, water management, telecommunications, tourism, town and country planning, or land use and which set the framework for future development consent of projects listed in Annexes I and II. The same applies to plans and programmes which, in view of the likely effect on sites, have been determined to require an EA pursuant to Articles 6 or 7 of the Habitats Directive (Directive 92/43/EEC). (Arts 2—3.)
Plans and programmes which determine the use of small areas at local level and minor modifications to plans and programmes which in themselves require an EA require an EA only where the Member States determine that they are likely to have significant environmental effects. Also with respect to other plans and programmes, which set the framework for future development consent of projects, the Member States must determine whether they are likely to have significant environmental effects.
Determining whether a plan or programme is likely to have significant environmental effects can be done either through case-by-case examination or by specifying types of plans and programmes or by combining both approaches. For this purpose Member States must take into account relevant criteria set out in Annex II, in order to ensure that plans and programmes with likely significant effects on the environment are covered by the Directive. The outcome of this determination, including the reasons for not requiring an environmental assessment when that is the case, is to be made available to the public.
The Court of Justice has made clear that an assessment of whether a plan or programme will require an EA pursuant to Articles 6 or 7 of the Habitats Directive is limited to the question of whether it can be excluded, on the basis of objective information, that that plan or project will have a significant effect on the site concerned. The same goes for areas referred to in Article 4(1) and (2) of the Birds Directive. 
In the case-by-case examination and in specifying types of plans and programmes the authorities likely to be concerned by the environmental effects of implementing plans and programmes by reason of their specific environmental responsibilities must be consulted.
Plans and programmes the sole purpose of which is to serve national defence or civil emergency, as well as financial or budget plans and programmes do not require an EA (Art 3).
An assessment carried out under the EIA Directive (Directive 2011/92/EU) does not dispense with the obligation to carry out an EA under the SEA Directive. However, if an assessment carried out under the EIA Directive were to comply with all the requirements of the SEA Directive there would be no obligation to carry out a new assessment pursuant to the latter Directive.35
Where a plan or programme has been adopted in breach of the obligation to carry out a prior EA, a court which has before it an action for annulment of such plan or programme is, in principle, obliged to take all the general or particular measures provided for by its national law in order to remedy the failure to carry out such an assessment, including the possible suspension or annulment of the contested plan or programme.36