From Ancilla Legislatoris to Ancilla Juris:
A Policy Brief on the Role of Comparative Law

It is beyond doubt that comparative law has a major significance for legal academia and practice. But what role does, and should, it play in detail? Legal academics as well as legal practitioners often understand comparative law as an “ancilla legislatoris,” that is, a subordinate “servant of the legislator” (Grundmann/Thiessen 2015): First, they claim that comparative research must serve legislation by producing findings useful for the process of amending old and creating new regulations de lege ferenda [I.]. Second, they subjugate comparative studies to the existing legislation regulating science and research de lege lata [II.]. My blog post, in contrast, will recommend both legislators and researchers to treat comparative law as an “ancilla juris,” that is, a “servant of the law” itself [III.].

I. One Objective: Ancilla Juris Instead of Ancilla Legislatoris

At first sight, it seems highly desirable for legislators to have comparative lawyers doing their legwork or even spadework. By researching the legal solutions in other countries and, ideally, their real-world implications, comparativists shall provide inspiration and insights to legislators. Indeed, comparative law can offer “useful lessons of how to [or not to] circumscribe claims to particular times and places, and how to study institutions that may interact with one another or serve as substitutes” (Linos 2018). In domestic legislation, such comparative advice merely offers an option of what to consider when drafting new or reforming old laws. In inter-, supra-, and multinational lawmaking and treatymaking, in contrast, it appears necessary and even natural to engage in legal comparisons—. Harmonizing national laws or drafting conventions that bind different nations requires mutually acceptable solutions and thus common ground between the countries involved. Therefore, for example, the EU resorts to legal comparisons—mostly between the laws of its 27 Member States—when creating supranational secondary legislation such as regulations and directives. Similarly, one single country’s—say, the United States’—legal and judicial cooperation with other countries should listen to comparative law, e.g., when drafting bi- or multilateral treaties. “[R]elevance to policymakers and practitioners” thus constitutes a “key goal for much of [comparative] legal research” (Linos 2018).

Consequently, so-called legislative comparative law (Zweigert/Kötz 1996), which focuses on the lex ferenda, traditionally has accounted for a fair share of legal comparisons (Donald 2008). In European academia, this phenomenon has often been interpreted as rendering comparative legal studies a mere “ancilla legislatoris” (Grundmann/Thiessen 2015). Such a conceptualization of comparative law as the “servant of the legislator” goes even further in other countries—e.g., in China, whose official ideology of Sinomarxism promotes the active transfer of foreign experiences (von Senger 1994). Sinomarxist theory demands Chinese law (as a research object, i.e., obiectum materiale) as well as legal studies (as a research discipline and method, i.e., obiectum formale) (see, Jestaedt 2007) to “adopt the others’ strengths to compensate their own [supposed] weaknesses” (“取长补短”). In this understanding, making foreign law and legal doctrine fruitful (or, some might say, exploitable) for the further development of China’s legal system becomes the ultimate purpose of comparing the law.

However, legislative comparative law concerned with the lex ferenda constitutes only one possible avenue for comparison. The much more common and important field in academia is so-called scientific-theoretical comparative law (Zweigert/Kötz 1996), which analyses the lex lata. Moreover, in legislative or in scientific-theoretical comparisons, comparative law should serve not the legislator but rather the law as such. In other words, comparative legal studies should always be understood as an “ancilla juris.”

This role as a “servant of the law” emanates from two considerations: First, serving the law means that (even legislative) comparative law yields relevance for much more areas, tasks, and institutions than legislation. Comparative insights are relevant not only when enacting and amending the law but also when interpreting or applying it. Put differently, they might be used not only by the legislative branch but also by the judicial branch, the executive branch, the legal profession, the parties to a lawsuit, and many more actors. Second, serving the law does not consign comparative legal academia to “servitude” under legal practice, i.e., under the abovementioned community of legal practitioners. Rather, serving merely signifies that comparative law provides them with “services.” Such services mostly consist in acts of knowledge production: Legal comparisons shall serve to better understand the law. For this cognitive and analytical purpose, comparative legal studies can and should also resort to knowledge that is not strictly legal in nature: on the one hand, to extrinsic aspects going beyond the horizon of positive legal stipulations; on the other hand, to theoretical considerations going above the imminent concerns of supposed practical necessities.

II. Two Obstacles: Under- and Overstating the Power of Comparative Law

When acting as an “ancilla juris,” there are many issues at stake for comparative legal studies (as a discipline and profession) as well as for comparative lawyers (as individual researchers). Two tendencies in legal academia and practice complicate the mission of serving the law and should thus be avoided:

1. Understating Comparative Law’s Potential

First, some comparative lawyers understate their own position and academic freedom. As supposed “servants” of the law, they argue that their comparative investigation process is bound to national law, particularly to the national regulations of scientific research. This argument would result in legislators dictating to comparative lawyers how to compare the law they enacted. However, its proponents overlook the difference between research in/within and research of/about a specific jurisdiction:

Obviously, legal researchers geographically located in a specific country are bound to respect that country’s laws and regulations—in a normative dimension. (Needless to say, this does not necessarily coincide with the factual dimension, i.e., does not mean that all academic jurists in fact do respect the relevant domestic legal rules. If one tried to conclude the latter factual statement from the former normative command, one would derive “is” from “ought” and thus commit a normative fallacy.) That the law demands obedience from the legal academy studying it can be observed in many different jurisdictions: For example, legal studies under German jurisdiction are required to adhere to the Basic Law (“Grundgesetz”), i.e., the German constitution (e.g., Böckenförde 1974; von Arnauld 2009), or at least to its basic principles of democracy, the rule of law, and human rights (e.g., Becker 2017). On Chinese soil, then, legal academics are actively and passively “reminded” to observe the censorship system (审查制度). Censors also request observance of domestic so-called “harmonization” rules from foreign science and scientists operating inside of China (see, Loubere/Ivan Franceschini 2018).

In contrast, the potential (!) justifications for these normative claims vanish as soon as the claims extend to mere non-domestic research about the respective country. Staying with the Sino-Western example: Chinese authorities increasingly try to apply their censorship rules also toward scientists that perform research about China but are located in other countries, such as France (e.g., Marsone 2020). Such extraterritorial claims must be rejected—at least in the realm of comparative studies. Otherwise, they would put researchers in an insolvable dilemma: Per definition, comparative law compares at least two legal orders. If we accepted the extraterritoriality of national regulations related to science, comparative lawyers would thus have to comply with the detailed rules of at least two jurisdictions. In many constellations, the details (though not necessarily the basics) of such domestic science-management stipulations vary heavily and even appear incompatible. For instance, if we subjugated comparative investigations between China and a German-speaking country to both national legal systems, these investigations would have to comply with expressly constitutionalist and liberal European regulations and explicitly anti-constitutionalist and illiberal Sinomarxism (e.g., Wang 2016; Gao 2012) at the same time—which is nothing less than impossible. The only solution to such a dilemma is rejecting the claims to extraterritoriality (extending to all details of our analysis) and instead seeking a compromise (limited to the basics of our research). Such a basic “least common denominator” between Chinese and German-speaking legal studies indeed remains possible because even between Sinomarxism and Euroliberalism, certain juristic methods and substantive concepts coincide and overlap, albeit merely formally or terminologically (see, Smith 2019).

2. Overstating Comparative Law’s Potential

Second, and in contrast, other comparative lawyers regularly overstate their own power—understood as politico-legal power and not as scientific knowledge-power (Foucault 1977). These jurists interpret the national law differently than the prevailing opinion and traditional doctrine—which is per se not a problem at all but rather a welcome sign of academic vitality and diversity. However, these comparativists draw their new interpretation of domestic law not from the domestic regulations as such (which follow their own rationale) but rather from foreign stipulations (which they compare the national regulation with). Yet, if we take the function of “ancilla juris” seriously, our comparative investigations, whether legislative or scientific-theoretical, should not try and change the law by themselves but rather support the institutions legally competent to do so. Indeed, there are various reasons for such a (supposed) self-limitation: From a legal theoretical perspective, law as well as legal studies are distinct from politics, including legal politics (Kelsen 2008). And from a rule of law (and potentially democratic) standpoint, legal academics must leave the task of changing the lex lata and enacting a new lex ferenda to the entities that the constitution has normatively designated (and, ideally, the constituency has democratically elected) for this task.

Under those premises, a common phenomenon in legal academia that prima vista seems uncontroversial or even beneficial can turn out to be problematic: hidden comparisons. This phenomenon occurs when legal investigations tacitly blur the boundaries between truly comparative research (typically between one’s own and a foreign legal system) and purely domestic analyses (either of one’s own or of a foreign legal system). In China, for example, it has been observed that “most legal scholarship in the post-Mao [era] is substantively comparative in some way, but very few scholars would consider themselves ‘comparative law scholars’ […], even as a secondary field. Much of this is simply due to neglect: few Chinese scholars would consider the use of foreign law as a reference point to be something that automatically falls under the methodological umbrella of ‘comparative law’—instead, it is how legal research is generally done” (Zhang 2019). Such hidden comparisons are common not only in Chinese legal studies but in many juristic traditions. But they become problematic in at least two constellations: First, as just mentioned, they can lead to interpreting national legal norms—in our example, Chinese regulations—in a certain manner that does not reflect domestic legal doctrine and thus the norms’ actual, positive legal content. Second, hidden comparisons might be used to smuggle doctrinal ideas and concepts or legal institutions and principles into national—in casu, Chinese—law that the latter does not recognize. 

At first sight, we might feel tempted to welcome this integration of comparative considerations in domestic legal research, because it seems to increase the importance and relevance of our discipline. Some might even argue that, from a substantive perspective, this integration precisely constitutes our legal academic contribution to the evolution or “enlightenment” of national law (especially if we are discontent with that law’s current state). Nevertheless, and from a formal point of view, as scientists, we are obliged to disclose what we are doing—i.e., that we are comparing and thus transcending the national dimension—in order to guarantee the scientificity of our research. Otherwise, our project might do more harm than good to legal science, and possibly also to the law it shall serve: At least in the two constellations outlined above, comparative lawyers try to circumvent the legislators or even aim at silently replacing them. Consequently, instead of serving the law, they serve themselves. And instead of serving the law, they ignore it or even tacitly try to bend and alter it. 

III. Three Recommendations: Valuing the Importance of Comparative Law

To sum up: Comparative law should strive for one objective—serving the law [cf. I.]—but may encounter two obstacles—understating or overstating its own power and freedom [cf. II.]. I recommend “law-makers” as well as “law-comparers” to manage these three dimensions by employing the following three policies:

First, comparative law must (be allowed to) serve the law and its better and deeper understanding. For this purpose, comparative studies need sufficient attention. Legal practitioners (legislators, courts, advocates, etc.) shall thus listen to legal academics (in casu, comparative legal researchers)—and vice versa. This dialogue will enable both types of actors to refute the all-too-common claims of “insurmountable rifts,” be it between different legal systems or between legal academia and practice. Regarding the former differences between legal orders and legal cultures, comparative law provides researchers as well as practitioners with arguments to refute the essentialist, ethnocentric, and (self-)Orientalist claim of peculiar “Chinese characteristics” of the P.R.C.’s legal system. Concerning the latter division between legal science and legal practice, comparative law scholars should strive to develop and employ so-called “practice theories.” Such theories combine scientific aspirations and practical needs because, in a dialectical process, practice can become the foundation of theory—and vice versa.

As a second recommendation, comparative law must not be subjugated (nor subjugate itself) to competing or contrarian legal requirements. Therefore, comparative studies need sufficient freedom. Research institutions and individual researchers should hence be allowed to perform research without burdening them with too many previously and centrally set aims. Although (or, some might say, precisely because) scientists analyze and compare the law without such concrete predetermined aims and thus in an open-ended manner, they do so with an overall purpose (see, Eser 1998). Their research is purposeful and meaningful as it produces and enhances knowledge about both other legal orders and their own legal system (see, Strathern 1988).

Third, comparative law must not (be forced to) disguise itself as purely domestic legal research. Not seldom, this problem is rooted in comparative jurist’s perception that they need to disguise what they are actually doing and love doing. One basic solution is simple: Political decisionmakers and science-managers should allocate sufficient funding explicitly for comparative research. Such funding needs not be limited to universities, because comparative research can also be performed in other institutions. Prime examples are independent centers like the ten law-related Max Planck Institutes in Germany and—soon not anymore (Zehnthöfer 2022)—Luxembourg or national state agencies such as the Swiss Institute of Comparative Law.

Taken together, these three recommendation can contribute to according comparative legal studies the position and status it deserves. They both demonstrate and ensure that for comparative law, serving the law as an “ancilla juris” is not a (self-)limitation but rather a (self-)liberation and empowerment.


von Arnauld, Andreas (2009), Die Wissenschaft vom Öffentlichen Recht nach der Öffnung für sozialwissenschaftliche Theorien, in Funke/Lüdemann (eds.), Öffentliches Recht und Wissenschaftstheorie, Tübingen: Mohr Siebeck, p. 65.

Becker, Florian (2017), The Development of German Administrative Law, 24 George Mason Law Review 453.

Böckenförde, Ernst-Wolfgang (1974), Grundrechtstheorie und Grundrechtsinterpretation, 27 Neue Juristische Wochenschrift 1529.

David C. Donald (2008), Approaching Comparative Company Law, 14 Fordham Journal of Corporate & Financial Law83.

Eser, Albin (1998), Funktionen, Methoden und Grenzen der Strafrechtsvergleichung, in Albrecht et al. (eds.), Internationale Perspektiven in Kriminologie und Strafrecht: Festschrift für Günther Kaiser zum 70. Geburtstag, vol. 2, Berlin: Duncker & Humblot, p. 1499.

Foucault, Michel (1977), Vérité et pouvoir (Interview), 70 L’arc 16.

Gao, Quanxi (高全喜) (2012), The Inception and Evolution of Political Constitutionalism (政治宪法学的兴起与嬗变),Shanghai Jiao Tong University Law Review (交大法学no. 1, p. 22.

Grundmann, Stefan and Thiessen, Jan (2015), Recht und Sozialtheorie im Rechtsvergleich. Interdisziplinäres Denken in Rechtswissenschaft und -praxis, in Grundmann/Thiessen (eds.), Law in the Context of Disciplines: Interdisciplinary Approaches in Legal Academia and Practice, Tübingen: Mohr Siebeck, p. 1.

Jestaedt, Matthias (2007), „Öffentliches Recht“ als wissenschaftliche Disziplin, in Engel/Schön (eds.), Das Proprium der Rechtswissenschaft, Tübingen: Mohr Siebeck, p. 241.

Kelsen, Hans (2008), Reine Rechtslehre: Einleitung in die rechtswissenschaftliche Problematik, Studienausgabe der 1. Aufl. 1934 (Jestaedt ed.), Tübingen: Mohr Siebeck.

Linos, Katerina (2018), Methodological Guidance: How to Select and Develop Comparative International Law Case Studies, in: Roberts et al. (eds.), Comparative International Law, New York: Oxford University Press, p. 35.

Loubere, Nicholas and Franceschini, Ivan (2018), How the Chinese Censors Highlight Fundamental Flaws in Academic Publishing, 3 Made in China Journal 22.

Marsone, Pierre (2020), « Censure » de l’expo « Gengis Khan » à Nantes : comment les dynasties « barbares » ont façonné l’empire chinois (Interview), L’Obs 12.10.2020,

von Senger, Harro (1994), Einführung in das chinesische Recht, München: C.H.Beck.

Smith, Ewan (2019), Socialist Law in Socialist East Asia (Book Review), 14 Asian Journal of Comparative Law 373.

Strathern, Marilyn (1988), The Gender of the Gift: Problems With Women and Problems With Society in Melanesia, Berkeley: University of California Press.

Wang, Tingyou (汪亭友) (2016), Western “Constitutionalism,” What Is Wrong [with You]? Analysis of the “Nuit debout” and the “Democracy Spring” Movements (西方“宪政民主”怎么了?——对“黑夜站立”“民主之春”运动的分析), Qiushi (求是) no. 13.

Zehnthöfer, Jochen (2022), Das Auslandsinstitut in Luxemburg wird geschlossen, Frankfurter Allgemeine Zeitung15.11.2022,

Zhang, Taisu (2019), The Development of Comparative Law in Modern China, in Reimann/Zimmermann (eds.), The Oxford Handbook of Comparative Law, 2nd ed., Oxford: Oxford University Press, p. 228.

Zweigert, Konrad and Kötz, Hein (1996), Einführung in die Rechtsvergleichung: Auf dem Gebiete des Privatrechts, 3rd ed., Tübingen: Mohr Siebeck.