Emilia Sandri

Introduction 

Mutual trust was designed for ordinary times. It presumes that Member States comply with EU law and with fundamental rights, and permits departures from that presumption only in “exceptional circumstances” (Opinion 2/13, para 191). Yet, a decade after Aranyosi and Căldăraru (Joined Cases C-404/15 and C-659/15 PPU) – the first case to allow exceptions to the execution of the European arrest warrant (EAW) on account of detention conditions – such refusals are no longer exceptional: they are a standing feature of judicial cooperation in criminal matters. The crisis that Aranyosi was meant to manage has become chronic. 

The European Court of Justice’s judgment of 4 June 2026 in Rugu and Aucroix (Joined Cases C-722/23 and C-91/24) confronts a question that this chronic condition was bound to produce: what happens to the sentence once surrender has been refused on fundamental rights grounds? The Court’s answer – that the executing Member State cannot invoke Article 4(6) of the Framework Decision (FD) on the EAW, but must instead activate the FD on the Transfer of Prisoners via its Article 4(5) – is doctrinally defensible. Beneath it, however, lie two moves this contribution analyses, because together they show how the Court responds when mutual trust fails empirically: it does not suspend the principle, but re-engineers it.  

Facts of the Case  

The joined cases arose from two Belgian refusals to surrender individuals sought through EAWs. Romania sought AR, a Romanian national residing in Belgium, for the enforcement of a four-year sentence (Case C-722/23); Greece sought HL, a Belgian national, for the enforcement of a five-year sentence (C-91/24). Both refusals rested on the national transposition of Article 1(3) of the FD on the EAW, finding a real risk of inhuman or degrading treatment contrary to Article 4 of the EU Charter on Fundamental Rights, on account of detention conditions in the issuing Member States. The courts then diverged: in AR’s case, the sentence was ordered to be served in Belgium, under the national transposition of Article 4(6) of the FD on the EAW – which permits refusal of surrender where the person is a national or resident of the executing Member State and that state undertakes to enforce the sentence domestically – while HL’s case did not consider Article 4(6) at all. The Cour de cassation referred both cases, asking whether an executing authority that has refused surrender under Article 1(3) must additionally apply Article 4(6) to enforce the sentence domestically. 

The Judgment and the Opinion of AG Rantos   

The Court answered both questions in the negative, in two steps. First, the grounds for non-execution cannot be combined. Article 1(3) is mandatory, applies irrespective of the person’s residence, and serves to protect fundamental rights, its application “necessarily puts an end to the surrender procedure” (para 43). Article 4(6) is optional, conditional on residence or nationality, plus an undertaking to enforce, and pursues a distinct objective: social rehabilitation (paras 47-48). Applying it “as a complement” to an Article 1(3) refusal “would result in disregarding the objectives pursued by each of those grounds as well as their respective nature” (para 52). The grounds are, in short, exclusive regimes.   

Second, the refusal does not exhaust the executing Member State’s obligations. Because the EAW mechanism seeks to combat impunity, the executing authority “is required actively to seek to ensure that the requested person does not go unpunished” (paras 55-57) through the FD on the Transfer of Prisoners. In fact, the fundamental rights refusal “does not affect the principle of mutual trust and mutual recognition with regard to the procedure which was lawfully conducted” (para 63), so nothing prevents recognition of the conviction. The executing Member State is therefore required to invoke Article 4(5) of the FD on the Transfer of Prisoners and request that the issuing Member State forward the judgment with a view to domestic enforcement (paras 68, 71). Although the Court itself acknowledges that Article 4(5) “does not create an obligation on the part of the issuing Member State to forward that judgment” (para 72), the latter’s discretion is heavily constrained: it must not bring mutual recognition “to a standstill” (para 73) and must “take due account” of the fact that a refusal would lead to impunity (para 74).  

AG Rantos proposed a different architecture. He saw no textual bar to cumulating the grounds, with the optional Article 4(6) of the FD on the EAW turning into an obligation channeled through Article 25 of the FD on the Transfer of Prisoners – which extends that FD’s provisions to the enforcement of sentences undertaken pursuant to Article 4(6)  of the FD on the EAW, “so as to avoid impunity of the person concerned” (paras 46–57, 72 of the Opinion). The Court’s route is thus formally stricter (no cumulation) but substantively softer: where the AG would have obliged the executing Member State to enforce, the Court obliges it only to actively seek enforcement through a request the issuing Member State may still refuse.  

Is Mutual Trust Severable?  

The first point of interest concerns the doctrinal move that makes the Court’s solution possible at all. Recognition under the FD on the Transfer of Prisoners is itself an exercise of mutual trust: Article 8(1) obliges the executing Member State to recognise the forwarded judgment save on exhaustively listed grounds. The route is thus only available if the Romanian and Greek judgments remain trustworthy – even though Belgium has judicially determined that surrender to those Member States would violate Article 4 of the Charter. The Court resolves this tension in a single paragraph: the refusal relates only to detention conditions, without affecting mutual trust in the lawfulness of the judicial proceedings themselves (para 63). Trust is therefore severable between the adjudicative process (which remains intact), and the enforcement conditions (where it is rebutted).  

On these facts, the divisibility of mutual trust is intuitive. Detention and adjudication are institutionally distinct functions, and neither AR nor HL challenged the fairness of their trials. Nor is this “compartimentalisation” new: since L and P (Joined Cases C-354/20 and C-412/20 PPU), the Court has held that even systemic deficiencies concerning judicial independence do not strip every court of the issuing Member State of its status as issuing judicial authority, nor dispense with an individualised assessment (paras 42, 59). If such deficiencies do not automatically taint every court, deficiencies in the detention conditions should not call into question convictions. The mechanism, moreover, does not ignore the established distrust but answers it: the sentence will be served in Belgian prisons, removing the very source of the Article 4 risk. Read this way, the judgment continues the Court’s strategy of disaggregating trust, so that cooperation survives its partial breakdown. From this perspective, L and P severed trust vertically, between the system and the individual court; Rugu and Aucroix severs it materially, between functions of the same criminal justice system.   

The vulnerability of this move lies not in its logic, but in its reach. The Court frames the anti-impunity duty attached to Article 1(3) refusals in general terms (para 57); yet the route through the FD on the Transfer of Prisoners works only where the ground of refusal leaves the conviction and the sentence intact. This is not always the case. Execution of an EAW may be refused where the conviction emanates from a court that was not independent or not established by law (see, for example, Puig Gordi (C-158/21)). Even the case law on the FD on the Transfer of Prisoners allows refusal to recognise a foreign custodial sentence on those grounds (see Staatsanwaltschaft Aachen (C-819/21)). Should the Court, in the pending Tagu case (C-583/24), accept that a manifestly disproportionate sentence can justify a refusal under Article 1(3) of the FD on the EAW, that would create another instance where the conviction itself is tainted. In neither scenario can the executing Member State simply assume enforcement without also committing a fundamental rights violation against the individual concerned. Yet, the judgment neither confines its duty to detention cases, nor explains what “actively seeking” enforcement requires where the judgment itself cannot be trusted or lawfully executed. It thus generalises a solution demonstrated only for a special case. 

A Duty Built from Discretions  

The second point concerns what the Court builds on that severance. Article 4(5) of the FD on the Transfer of Prisoners is, on its face, among the most modest provisions in the instrument: the executing Member State may request the judgment, and such requests “shall not create an obligation of the issuing State” to forward it. The Court transforms this double discretion into the mandatory anti-impunity mechanism of the EAW system. The executing Member State must make the request (para 71); the issuing Member State, “when considering refusing”, must take due account of the resulting impunity and must not bring mutual recognition to a standstill (paras 73–74). A duty is assembled from a provision the legislature drafted as an option.  

The Court’s rationale is understandable: no provision of the FD on the EAW determines the consequences of an Article 1(3) refusal for the enforcement of the sentence (para 44). This is a genuine, crisis-shaped, legislative gap. The legislature never regulated the aftermath of a fundamental rights refusal because it never anticipated that systemic rights failures would become a standing feature of the Area of Freedom, Security and Justice (AFSJ). Faced with such a gap, the Court repurposed an instrument designed for social rehabilitation into an impunity-avoidance mechanism, holding that rehabilitation itself “requires the sentence actually to be enforced” (para 67). Yet, that equivalence is not obvious: rehabilitation does not logically presuppose punishment, nor does combating impunity necessarily require enforcement through a rehabilitation instrument.  

Two difficulties follow. The first is textual: Article 4(5) says a request “shall not create an obligation” on the issuing Member State to comply. Yet the Court holds that the issuing Member State’s refusal is lawful only if it has duly weighed the resulting impunity and avoided bringing recognition to a standstill – conditions that leave the “no obligation” clause with little practical scope. The second is practical. AG Rantos would have obliged the executing Member State to enforce; the Court requires it only to ask. But what if the issuing Member State – whose detention conditions have just been judicially condemned by the very Member State now requesting its judgment – declines or ignores the request? The judgment presumes good faith and sincere cooperation (paras 58–59) from the Member State whose compliance is in doubt, and offers no remedy beyond the shadow of Articles 258–259 TFEU. The requested person, meanwhile, remains in limbo: not surrendered, not yet serving the sentence, and dependent on an inter-State dialogue with no deadline and no sanction. 

Conclusion  

The two moves are connected: the Court needs to sever mutual trust to make the Article 4(5)-route viable, because recognition presupposes that the judgment remains an object of trust. Severance comes first; the duty built from discretions stands on it. Together, they re-engineer mutual trust: rather than abandoning or restoring it as its grounds erode, the Court redesigns the principle, dividing trust into different functions and converting discretions into judicially enforced duties, allowing cooperation to continue. Whether this structure is sound is another matter. A system where preventing impunity depends on the goodwill of the defaulting Member State, and where trust survives only through ever-finer disaggregation, may avoid a standstill today at the cost of normalising the deficiencies that triggered refusal. Rugu and Aucroix keeps the machinery of the AFSJ running, but its limits once trust is rebutted on grounds other than detention conditions remain to be tested.