Normative conflicts (antinomies) are a traditional topic in Western legal thought [1]. The term, quite broadly speaking, refers to the situations in which two legal norms, simultaneously applicable to the same state of affairs, regulate the state of affairs in a mutually incompatible manner.
Example 1:
Norm N1 “Abortions are prohibited.”
Norm N2 “Abortions are permitted in cases of medical emergencies.”
Two norms conflict with respect to abortions in cases of medical emergency.
Example 2:
N1 “It is prohibited to stop cars in front of military bases.”
N2: “It is obligatory to stop cars in red lights.”
Two norms are in conflict regarding red lights that are placed in front of military bases.
The theory of normative conflicts is usually divided into two broad areas (Bobbio 1988: 123). The first issue is the question of their identification, which includes their definition, typologies and relations to interpretation and argumentation. The second issue concerns their resolution, specifically the identification of criteria for resolving normative conflicts. The criteria have the function of determining which of the conflicting norms will prevail and in what way (Chiassoni 2011, 282).
In addition to lex superior derogat legi inferiori (a hierarchically higher norm prevails over the lower) and lex specialis derogat legi generali (a special norm prevails over the general norm), one of the traditional criteria for resolving conflicts of norms is the criterion lex posterior derogat legi priori, according to which the norm that was introduced later into the legal system “prevails” over the norm that was introduced earlier. For this reason, the criterion is usually regarded as the mechanism by which implicit (or tacit) derogation (repeal) – the elimination of the norm from the legal system – operates.
While the explicit derogation of a norm occurs after the norm-giver enacts a norm of explicit derogation (“The provision P is derogated.”), the implicit derogation occurs due to the incompatibility of the earlier and the later norm, and the lex posterior criterion [2]. Thus, the use of the lex posterior criterion to establish that a norm has been derogated is considered a part and parcel of judicial function, meaning that every court is competent to use it when answering a questio iuris relevant to the solution of a particular case [3].
A common discussion on the topic of lex posterior criterion is the issue of its necessity in legal systems. The issue, more precisely, revolves around the question: “Is the lex posterior criterion a necessary (in some yet to be determined sense) feature of legal systems? Do legal systems necessarily contain it?”
The remainder of this blog post will offer a brief sketch of the theoretical terrain on this issue, outlining both the positive and negative answers to the question and some prominent authors who have argued on both sides.
The necessity thesis
The affirmative answer to this question is called the thesis of necessity. In the history of legal thought, the thesis of necessity has taken two different forms, depending on the meaning of “necessity” attributed to the criterion of lex posterior: the logical necessity thesis and the conceptual necessity thesis.
The logical necessity thesis
The first one version of the necessity thesis is mostly associated with the so-called Begriffjurisprudenz of the 19th century. This version states that for logical reasons, usually pertaining to the logical law of non-contradiction, the existence of lex posterior is a logically necessary element of (modern) legal systems. In other words, because the logical law of non-contradiction prohibits the simultaneous existence of the two contradictory norms in the same legal system, the later norm must prevail or be taken to be the only one “genuinely” existing in the system.
A summary of the view is presented nicely by the Austrian legal philosopher Hans Kelsen, who, in his “early phase”, advocated for the view of lex posterior as a “juridico-logical” principle. Thus, Kelsen claims that:
That a later norm invalidates an earlier norm when the content of the one contradicts that of the other and furthermore, that the later norm in place of the earlier one lays down a particular course of conduct as obligatory – this of course counts as a juridical-logical principle only within a unified normative system. […] The general logical tenet that judgment A is incompatible with judgment non-A is different from the logical principle peculiar to normative cognition. According to the latter, it is not the case that either norm A or norm non-A can be valid, as is the case with judgments, where either judgment A or judgment non-A is true. Rather, what distinguishes the specific logical principle of normative cognition is that only the later norm can be valid, given that the norms in question belong to the same system. The requirement that the later norm take precedence over the earlier norm and not the other way around is a purely logical consequence that follows from the nature of the norm and from the essence of unity in the normative system
(Kelsen 1914: 206-7 – the emphasis is mine)
Two main counterarguments are levelled against this view [4]. First, although the view that the contradiction between two norms cannot be admitted is perhaps defensible, the claim that this logically implies that the later norm must prevail is simply a non-sequitur, since the contradiction could just as well be evaded by adopting the lex prior principle, according to which the earlier norm prevails. Second, and adding fuel to the previous argument, the lex posterior principle is clearly not applicable to all normative conflicts. Indeed, it is often defeated by other criteria such as lex superior and lex specialis, opposite of what one would expect from a “logical” principle [5].
As a result, the logical necessity thesis is nowadays widely rejected by contemporary legal theory [6]. Despite this, the lex posterior is still, although probably quite unreflectingly, often described as a “logical” principle in everyday juristic discourse [7].
The conceptual necessity thesis
The necessity thesis has experienced somewhat of a surge in popularity in recent decades as its second version, which we dub the conceptual necessity thesis, has been defended by several prominent legal theorists [8].
On this version of the claim, the lex posterior is held to be a conceptually necessary feature of legal systems. Thus, rather than pertaining to necessity as a matter of the principle of non-contradiction, this version of the claim holds that the necessary existence of lex posterior conceptually follows from the (conceptually necessary) nomodynamic nature of legal systems [9]. The argument is nicely summarized by legal philosophers Carlos E. Alchourrón and Eugenio Bulygin:
This rule [lex posterior] is conceptually linked to the notion of competence if by ‘competence’ we understand the faculty of changing the normative status of certain actions. Therefore, the rule lex posterior is not a contingent rule. Rather, it is conceptually necessary in so far as there is a norm-authority who is competent to change the deontic qualifications of certain actions. […] Without the rule lex posterior, however, there would be no competence at all, and then there would be no possibility of normative change emerging from acts of authority.
(Alchourrón & Bulygin 2015: 326 – the emphasis is mine)
The main counterargument to the claim invokes the already mentioned distinction between explicit and implicit repeal [10]. Even if we assume that the nomodynamic nature of law conceptually requires that the normative authority can repeal a norm, it does not necessarily imply that the authority must have the ability to do so implicitly. The authority might, after all, have only the capacity to repeal the norm explicitly [11]. In short, the nomodynamic nature of law conceptually requires the existence of the mechanism of repeal, but not necessarily the mechanism of implicit repeal. And since only implicit repeal, but not explicit repeal, presupposes existence of the lex posterior, it follows that the nomodynamic nature of law does not necessarily imply the existence of the lex posterior in a legal system.
Although this counterargument presents a blow against the conceptual necessity thesis, the debate on the issue is surely going to continue, as arguments on both sides are restated and refined [12].
The content of this blog post is related to my ongoing PhD Thesis, “The Traditional Criteria for Resolving Normative Conflicts”.
SUGGESTED CITATION: Relac, Svan: “Is Lex Posterior Necessary in Legal Systems?“, FOLBlog, 2025/09/19, https://fol.ius.bg.ac.rs/2025/09/19/is-lex-posterior-necessary-in-legal-systems/
NOTES
[1] Some of the influential classics on the topics of normative conflicts include Bobbio 1960; Engisch 1956; Gavazzi 1959; Kelsen 1960; Perelman 1965.
[2] On the distinction, see, e.g., Guastini 2017.
[3] As opposed to the lex superior criterion, the use of which to establish that a norm is invalid and thus annulled is commonly reserved only for some specialized courts of the legal system.
[4] See, among many García Máynez 1963: 9.; Paulson 1983: 9.
[5] It is usually considered that the later inferior norm (e.g., a law) will never prevail over the earlier superior norm (e.g., the constitution). Moreover, it is sometimes considered that even the earlier but special norm prevails over the later general norm. See, e.g., Bobbio 1988: 133-135.
[6] Kelsen himself, adopting the views of his Viennese colleague Adolf Merkl, seems to have rejected them in the 1920s. On Kelsen’s changing views on the lex posterior, see Paulson 1983. For Merkl’s rejection of these early Kelsenian views, see Merkl 1918.
[7] See, e.g. Croatian Constitutional Court Case U-I-7217/2021 of December 20th 2022; Some introductory textbooks to legal philosophy or legal reasoning take the lex posterior criterion to be logical or “systemic-logical” methods of interpretation. See, e.g. Kirste 2020: 54-55.
[8] Including Carlos Alchourrón and Eugenio Bulygin (2015: 326), Pablo E. Navarro and Jorge Rodríguez (2014: 223 and 2015: 112) and Luigi Ferrajoli (2016: 649).
[9] In contemporary legal theory, especially following the works of Hans Kelsen and HLA Hart, it considered is noncontroversial that a distinguishing feature of contemporary legal systems is their ability to undergo deliberate change on behalf of competent authorities. See Kelsen 1934, esp. ch 5. Hart 1961, esp. ch. 5.
[10] An early version of this argument was advanced by Merkl 1918: 82-83. A modern version of the argument is made by Guastini 2017.
[11] Such a legal system could have two general models of dealing with normative conflicts between the earlier and later norms. The first is a model in which the lex prior criterion applies, according to which the court is competent to determine that in a conflict the earlier norm prevails over the later one. The second is the model in which the court, having established a normative conflict between an earlier and a later norm, is obligated to ask the legislature to (explicitly) confirm the repeal of the earlier norm.
[12] One example of a sophisticated refinement of the necessity thesis is advanced by Agüero-SanJuan 2017.