Ellipsis in the sense of leaving the noun out of a phrase that consists of a noun plus an adjective is common in Spanish. For example, people refer to a tarjeta postal (post card) as simply una postal. Other common examples include referring to a tren expreso (express train) as un expreso (which an English reader might take to be a kind of coffee drink) and calling a página web simply una web (which an English reader might understand to be the Internet itself, instead of merely a page on it). Visite nuestra web means "visit our website" not "visit our intranet" or something like that.
It seems to me that this kind of ellipsis (which involves using adjectives as nouns) rarely occurs in English. Instead, in English we tend to have phrases that consist of two nouns (like "microwave oven") and drop one of the nouns (referring to it as the "microwave"). Be that as it may, the use of stand-alone adjectives in legal Spanish can be particularly confusing to an unitiated reader, because he or she will have to be able supply the missing noun in order to understand the phrase or look it up in the dictionary.
Here are some examples of this kind of ellipsis in legal Spanish:
Court names. The Tribunal Supremo is Spain is often referred to as el Supremo, and the Tribunal Constitucional is called el Constitucional.
Criminal law. Circunstancias atenuantes (extenuating circumstances) are referred to as las atenuantes; circunstancias eximentes (exculpatory circumstances) can be called las eximentes and circunstancias agravantes (aggravating circumstances) can be called las agravantes.
Evidence. The names of the various types of evidence (prueba) are often referred to without using the noun prueba. Therefore:
La testifical is la prueba testifical.
La confesional is la prueba confesional.
La documental is la prueba documental.
La pericial is la prueba pericial.
Ministries. A recent headline announced Exteriores anuncia un redespliegue de la red consular por todo el mundo. Here, Exteriores is obviously an ellipsis for Ministerio de Asuntos Exteriores (Ministry of Foreign Affairs).
Taxes. In the sentence Este año hemos integrado en los recibos de la urbana el de la tasa de basuras "la urbana" is a short-form of contribución urbana.
Judges. The juez instructor (investigating magistrate) in a criminal court may be referred to simply as el instructor. This strikes me as especially tricky because an English-speaker who is asleep at the switch could understand instructor to be the English word "instructor" (docente, profesor or even instructor in Spanish), which would be completely out of place in the criminal procedure context.