Règle correspondante
Spain
Practice Relating to Rule 8. Definition of Military Objectives
Section H. Areas of land
Spain’s LOAC Manual (1996) states:
The capture or preservation of a specific area of land constitutes a military objective when it meets all the requirements laid down in Article 52 of Additional Protocol I and it confers a concrete military advantage taking into account the circumstances ruling at the time. 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Publicación OR7-004, 2 Tomos, aprobado por el Estado Mayor del Ejército, Division de Operaciones, 18 March 1996, Vol. I, § 4.4.d; see also § 2.3.b.(1).
Spain’s LOAC Manual (2007) states:
Taking or holding a certain area of land is considered a military objective, when all the requirements laid down in article 52 of [the 1977] Additional Protocol I are met and it provides a concrete military advantage, taking into account the circumstances prevailing at the time. 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Tomo 1, Publicación OR7–004, (Edición Segunda), Mando de Adiestramiento y Doctrina, Dirección de Doctrina, Orgánica y Materiales, 2 November 2007, § 4.4.d; see also §§ 2.3.b.(1) and 4.2.b.
The Report on the Practice of Spain (1998) notes that the fact that a particular zone may be considered a military objective provided it fulfils the requirements of Article 52(2) of the 1977 Additional Protocol I is consistent with the possibility provided for under Spanish law of establishing zones of interest for national defence, comprising “expanses of land, sea, or airspace declared as such because they constitute or may constitute a permanent base or an effective aid to offensive action necessary for such purpose”. 
Report on the Practice of Spain, 1998, Chapter 1.3, referring to Zones and Installations Law, 1975, Article 2.
Upon ratification of the 1977 Additional Protocol I, Spain stated:
It is the understanding [of the Spanish Government] that the capture or holding of a specific area of territory constitutes a military objective when all the conditions set out in this paragraph [paragraph 2 of Article 52] together offer a concrete military advantage taking into account the circumstances at the relevant time. 
Spain, Declarations made upon ratification of the 1977 Additional Protocol I, 21 April 1989, § 7.