These terms are clearly “false friends.” In English “legitimation” is a family law term, generally referring to the legitimation of an illegitimate child through the marriage of their parents or, in jurisdictions where it is required, acknowledgment by the child’s father. In Spanish family law, voluntary legitimation of a nonmarital child is expressed as reconocimiento de paternidad (“acknowledgment of paternity”), but may also be the result of an acción de filiación (“paternity suit”) in which a sentencia firme de paternidad (“paternity judgment;” “judgment of paternity”) has been rendered.

In contrast, in Spanish legitimación is a totally unrelated civil procedure term that is often mistranslated literally as “legitimation.” In this context legitimación actually refers to what in Anglo-American law is termed “standing” (or locus standi), i.e., the right to bring an action or to challenge a decision in court. Thus legitimación procesal is “standing to sue or be sued,” while legitimación activa specifically describes the “plaintiff’s standing” or “standing to sue,” while legitimación pasiva is the “defendant’s standing” or “standing to be sued.” In this context, excepción de falta de legitimación is a “motion to dismiss for lack (or) want of standing”. And, in an additional example from Spanish inheritance law, legitimación para pedir la partición denotes “standing to demand the division of an inherited estate” among the coheirs.

In other contexts legitimación may likewise denote “authentication.” Thus an expression such as legitimación de la firma refers to “authentication of a signature” or “signature authentication.” And legitimación de capitales is sometimes used as a synonym for blanqueo de capitales (“money laundering”).

Thus, in the examples shown above legitimación cannot be appropriately rendered as legitimation. But can legitimación perhaps be translated as “legitimacy”? I’ve found at least one instance in which this may be possible: when referring to land registration legitimación registral may perhaps be rendered as “legitimacy of registration,” being the presumption that entries on the Registro de la Propiedad are accurate and that rights recorded on the register actually belong to the registered titleholder.