Amicus curiae


Author Definition



Amicus Curiae stands for “friend of the court”, also known in some jurisdictions as a “third-party intervention”, that is to say someone who is not a party to the litigation, but who intervenes in the proceedings to enlighten the sitting judges and influence the outcome of a lawsuit involving matters of public interest by providing their external analysis regarding questions of law or fact in their area of expertise. The entity assuming this role can be a Governmental representative, a public institution or agency, an interest group established or not as an NGO, a company, a law firm, a university professor that believes that the court’s decision may affect its interests.



Amicus Curiae, an expression whose first known use is dated in the early 17th century UK, is a concept that authorities and courts have carefully avoided to strictly determine the perimeters and conditions justifying its use. The Amicus is not a litigating party, provides information on areas of law that the court regards as complex and beyond its expertise, and can also represent third party interests that could be ignored under adversarial court systems.

The practice of submitting Amicus Curiae briefs is well established in common law jurisdictions, has become common practice within international cooperation organizations, within arbitral tribunals in matters of investment arbitration and is largely used in competition cases in the US and more recently in the European Union. It is important to note that civil law jurisdictions do not have a tradition in using such an instrument and its introduction is mostly recent.

In the US antitrust enforcement of the last decades, it is extremely interesting to notice that concerning Foreign States’ Amicus Curiae participation, the European Commission emerges as the most frequent Amicus filer in front of US Courts, followed by Canada and Japan. So, it should not come as a surprise that this instrument was progressively also introduced in EU Competition Law enforcement on the initiative of the same EU institution.

Why did the use of Amicus briefs in antitrust cases flourish in the US? The main characteristic of the US antitrust system, as observed from abroad and more specifically from the EU, is the fact all decisional power relies in the hands of Judges and not the governmental antitrust agencies. Non-expert judges are called, since the Sherman Act, to decide complex technical and economical questions relating to industrial organization. The traditional methods of decision-making based on precedent, analogy, intuition and considerations of morality and efficiency have quickly lagged behind the increasing needs of antitrust litigation.

That is where Rule 37 of SCOTUS, referring to the year 1937 codified rules about amicus participation, started to play an important role, allowing Justices to look for technical help in understanding economic theory and interpreting empirical data on competition. Unsurprisingly, these amicus briefs receive considerable attention from the Court and influence its opinions. The Court’s increased interest in amicus arguments coincided with the rise of legal realism, which rejected the idea that judges discover law as a scientist discovers physical properties of the universe. As the Court began to realize its role to be policy making, access to information about the effects of that policy became necessary to make rules responsive to social needs.

Formally, an amicus in the US must get permission from either the parties or the Court to file a brief, but the Court’s current practice is to grant nearly all motions for leave to file as amicus curiae when consent is denied by a party. As a result, ninety-five percent of cases filed before the Supreme Court between 1996 and 2003 included at least one amicus brief while the influence of Amicus briefs on Supreme Court decisions is considered significant and often explicitly cited in the judgment or a dissenting opinion. (Omari Scott Simmons, Picking Friends from the Crowd: Amicus Participation as Political Symbolism, 42 CONN. L. REv. 185, 193 (2009); Joseph D. Kearney & Thomas W. Merrill, The Influence of Amicus Curiae Briefs on the Supreme Court, 148 U. PA. L. REv. 743, 828-30 (2000)).

This is the opposite of the rationale of EU competition law and policy, since the European Commission is entrusted with full decision-making powers, and as a governmental agency includes a full Economist Team and a well-established process of consulting the industry during the legislative phase. Once adopted, an administrative decision of the European Commission can only be appealed before the General Court of the EU in Luxembourg. This is probably the main explanation on why the amicus curiae, although introduced in EU antitrust, is not as developed nor influential. Nevertheless, in front of the EU Courts, competitors or NGO’s may be permitted to introduce briefs as “intervening parties”. A fundamental difference with the US is that EU Courts still exercise a very strong scrutiny on the usefulness of such an intervention, while EU Members States or EU institutions can always intervene if they wish since the EU Treaties grant them directly this benefit.

The recent rise of private enforcement of EU Competition Law, in particular cartel damages claims following Directive 2014/104/EU, has resulted in the Amicus Curiae mechanism becoming crucial to the system. Article 15(3) of EU Regulation 1/2003 established it as the cooperation mechanism between the Commission, the national competition authorities and the courts of the Member States, in order to ensure the coherent application of EU competition rules in the 27 EU Member States and jurisdictions. This is part of the general principle of sincere cooperation, which is of particular importance where that cooperation involves the judicial authorities of a Member State which are responsible for ensuring that EU law is applied and respected in the national legal system. The mechanism of the Amicus Curiae gives the the European Commission the opportunity to show its good faith and sincere cooperation towards Member State’s Judges.

Despite these positive theoretical considerations, national judges have so far made limited use of obtaining an Amicus brief from the Commission. An explanation could be that judges are reluctant to be advised by an administrative body, or the reluctance may be because the judge is not so familiar with the procedure. In fact, despite the crucial role given to national judges, one must still keep in mind that the final word about the application and interpretation of the EU law, including all competition rules, remains in the hands of the EU Court of Justice, via the preliminary ruling procedure established by article 267 TFEU. In fact, any national court may refer a question to the CJEU on the interpretation of a rule of EU law if it considers it necessary to resolve a dispute brought before it and national judges have a long positive experience with this procedure. Nevertheless, the Amicus mechanism is used increasingly together with the Preliminary reference, thus showing a complementarity that pursues the effectiveness of articles 101 and 102 TFEU all over the EU. However, obtaining an Amicus Curiae legal opinion from the Commission could be faster than a reference to the CJEU and probably should be more used by national judges. Indeed, the Commission, in its non-binding observations, generally refers to the case law of the CJEU and its own decisions as useful indications of the criteria and the type of evidence that have been taken into account in similar cases.



Gerlich, O, More than a friend? The European Commission’s amicus curiae participation in investor-state arbitration, in: G Adinolfi et al. (Eds.), International economic law, Springer 2017, pp. 253–269.

Haw Allensworth R., Amicus Briefs and the Sherman Act: Why Antitrust Needs a New Deal, 89 Texas Law Review. 1247 (2011).

Kearney, Joseph D., and Thomas W. Merrill. “The Influence of Amicus Curiae Briefs on the Supreme Court.” University of Pennsylvania Law Review, vol. 148, no. 3, 2000, pp. 743–855.

Vallindas G., Amicus Curiae: An overview of EU and national case law, 15 November 2018, e-Competitions Amicus curiae, Art. N° 87106.

Wiik, A., Amicus Curiae before International Courts and Tribunals (pp. 707–734). Baden-Baden: Hart/Nomos (2018).


  • European Court of Justice (Luxembourg)


Georges Vallindas, Amicus Curiae, Global Dictionary of Competition Law, Concurrences, Art. N° 85868

Visites 1434

Publisher Concurrences

Date 1 January 1900

Number of pages 500


Institution Definition

Pursuant to Article 15(3) of Regulation 1/2003, the Commission, acting on its own initiative, may submit written observations ("amicus curiae" observations) to courts of the Member States where the coherent application of Article 101 or 102 TFEU so requires. © European Commission

On this topic, see the e-Competitions special issue "Amicus curiae: An overview of EU and national case law"

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