Does MASC Apply to Arbitration? Spanish Courts Disagree

“It was the best of times, it was the worst of times, […] it was the epoch of belief, it was the epoch of incredulity” wrote Charles Dickens at the opening of A Tale of Two Cities (1859). Spanish arbitration is having its own tale of two cities. In Zaragoza first and now in Oviedo, two High Courts of Justice (in Spanish a Tribunal Superior de Justicia or “TSJ”) have, within little more than three months of each other, taken opposite views on whether the new pre‑action negotiation requirement of Ley Orgánica 1/2025 (“LO 1/2025”) applies to arbitration‑related court proceedings.

As explained in a previous post (see Blog post here), LO 1/2025 introduced into Spanish civil procedure a general obligation to attempt a Medio Adecuado de Solución de Controversias (“MASC”) before filing civil and commercial claims. MASC is broadly defined as any good-faith effort to reach an extrajudicial settlement (mediation, conciliation, a neutral expert opinion, a confidential binding offer or any equivalent process). Under Article 5 LO 1/2025, the requirement operates as a pre‑action condition of admissibility, the claimant must show either that a prior attempt at negotiation was made or why none was possible. Article 5.2 then sets out a list of exceptions, which omits any reference to arbitration‑related court proceedings.

That silence has not gone unnoticed by the TSJs.

The TSJ of Aragón was the first to fill the gap (“Aragón’s decision”), engaging with a MASC objection on the merits in an annulment action and thereby implicitly treating the requirement as applicable to set‑aside proceedings. The TSJ of Asturias (the “Asturias Court”) has now drawn the opposite line in its Judgment nº2/2026 of 23 March 2026 (the “Asturias’ decision”), expressly rejecting MASC as an admissibility filter for actions to set aside an arbitral award under Spain’s Arbitration Act (the “AA”). Where Aragón opened the door, Asturias has firmly closed it on three distinct grounds. This post analyses the Asturias’ decision, compares it with Aragón’s decision and locates the source of the problem in the legislation itself.

Three Reasons Why MASC Has No Place in Annulment Proceedings

A brief word on the facts. Logística Transitaria Marítima, S.L. (“Logística”) brought an action to set aside award nº 145/2025 of 29 October 2025, issued by the Junta Arbitral de Transporte del Principado de Asturias (a regional arbitration body competent to hear commercial claims arising from transport contracts) against Intercolpen, S.L. (“Intercolpen”). The award resolved a dispute over storage charges connected to a maritime transport operation, which Logística then sought to set aside.

Logística invoked a single ground, the alleged breach of public order under Article 40.1.f) of the AA, arguing that the award was arbitrary because it had ignored a determinative fact (an acknowledgment of debt by Intercolpen in an email exchange). Intercolpen’s first line of defence was a preliminary objection that Logística had failed to comply with Article 5 LO 1/2025 because no prior MASC attempt had taken place before filing. As the prior Blog post explained, annulment actions in Spain are channelled through a civil claim form before the TSJs of each Autonomous Community.

The Asturias Court dealt with that objection as its very first legal ground and dismissed it for three reasons.

Firstly, the Asturias Court holds that the MASC requirement under Article 5 LO 1/2025 is confined to declaratory proceedings under Book II of the Spanish Civil Procedure Act and that the list of exceptions in Article 5.2 is illustrative, not exhaustive. If it were a numerus clausus, MASC would be a precondition even for proceedings whose function runs against it. Other proceedings whose nature collides with the MASC rationale should therefore also be left out.

Secondly, annulment under Article 40.1.f) of the AA invokes public order, and public order is, by definition, non-negotiable. It cannot be the object of mediation, conciliation or any negotiated outcome, which is precisely why the legislator lists it as a ground for annulment. As the Asturias Court puts it, it would not be viable to submit an alleged breach of public order to negotiation or settlement.

Lastly, and perhaps most interestingly, the Asturias Court adds that an arbitral award already presupposes that the parties have resorted to an alternative dispute resolution (“ADR”) mechanism. Requiring a MASC attempt before annulment would force the parties into a second round of ADR simply to attack the outcome of the first. Crucially, this third reason does not depend on the ground invoked: it keeps MASC out of the set-aside actions whatever the basis of the challenge; whether public order, invalidity of the arbitration agreement, lack of arbitrability or any other ground listed in Article 40.1 of the AA.

Taken together, these three reasons amount to a firm rejection of MASC as an admissibility filter for annulment. Yet just three months earlier the TSJ of Aragón had reached the opposite conclusion on essentially the same question.

Two Spanish High Courts, Two Opposite Answers on MASC

The TSJ of Aragón’s Judgment nº17/2025 of 12 December 2025 was the first Spanish decision to engage with a MASC objection in an annulment action. The respondent argued that the claim should be dismissed because no prior negotiation had been attempted. What matters is that the TSJ of Aragón did not reject the objection as inadmissible. It examined whether a negotiation effort had taken place, found on the evidence that it had and proceeded to the merits. By engaging with the objection on its own terms, it implicitly accepted that LO 1/2025 operates as an admissibility filter for annulment actions.

The same procedural question, raised three months later in a similar case, was met with three reasons to reject MASC as an admissibility filter altogether. The contrast with Asturias could not be clearer.

On the treatment of the MASC objection, the TSJ of Aragón engaged with it on the merits and assessed whether a prior negotiation had taken place, whereas Asturias rejected it in principle without examining the facts.

On the reasoning, Aragón offered nothing on applicability and simply assumed that Article 5 LO 1/2025 applies to the annulment of an arbitral award. Asturias, by contrast, rested its rejection on the three reasons set out above. The practical consequences are the exact opposite. Under Aragón, respondents are incentivised to raise MASC as a threshold defence and admissibility becomes a front-loaded battleground. Under Asturias, the objection should be dismissed and the merits are reached without procedural detour.

The two TSJs faced essentially the same question and gave opposite answers, with Asturias having had the benefit of Aragón’s decision and choosing not to follow it. The previous post predicted this divergence. Annulment is heard before seventeen different TSJs and they were always going to disagree until the Spanish Supreme Court steps in.

Whether the MASC requirement applies to an action to set aside a Spanish-seated award now depends on the geography of the seat. A party challenging an award rendered in Zaragoza must prepare for a threshold MASC fight; one challenging an award rendered in Oviedo can expect that fight to be dismissed before it begins.

Geography Should Not Decide Admissibility

Asturias’ answer is, quite frankly, the logical approach to take.

Satellite litigation on MASC is here to stay even where the Asturias line prevails. Respondents in annulment proceedings have every incentive to raise the objection regardless of the merits, because raising it costs little. Even if the objection is dismissed it will have consumed time and resources and shifted the centre of gravity of the proceedings away from the actual grounds for annulment and towards an exchange on whether something resembling a negotiation attempt was made. Annulment proceedings are supposed to be exceptional, swift and confined to a closed list of grounds. The system does not need an extra fight at the door.

Yet Asturias’ decision does not close the door on every variant of the MASC objection. The first reason offered by the Asturias Court is a general doctrinal point but it requires a further analytical step; identifying which other proceedings are sufficiently incompatible with the MASC rationale to be left out (such as urgent summary proceedings, as requiring a prior attempt would defeat the very purpose of the summary protection). The second reason is tied to Article 40.1.f) of the AA and does not dispose of annulment actions brought on other grounds such as the invalidity of the arbitration agreement, the lack of arbitrability or irregularities in the constitution of the tribunal. Only the third reason supplies a general basis to exclude MASC before an annulment action regardless of the ground invoked. Whether other TSJs will embrace the Asturias Court’s reasoning or quietly ignore it is the next open question and, in my view, the question to watch over the coming months.

None of this should have been left to the TSJs in the first place. The whole controversy is the product of a legislative silence, the omission of any reference to arbitration-related court proceedings from LO 1/2025’s exclusion list. The cleanest fix is also a legislative one. A short carve-out, whether inserted in LO 1/2025 or in the AA, would end the debate and spare arbitration users the spectacle of seventeen TSJs working out what the legislator did not bother to clarify.

Until that fix arrives, Spanish arbitration will continue to live its tale of two cities. For now, in Spanish arbitration the city you choose decides whether you believe or whether you doubt.