On 24 March 2026, Spain’s Supreme Court handed down Judgment No. 368/2026 (appeal 5782/2023, ECLI:ES:TS:2026:1875) in the so-called “Cables BT/MT cartel” case. The ruling addresses two questions of major significance for competition law enforcement in Spain: how time gaps between anticompetitive episodes should be treated when a common plan exists, and what criteria the competition authority may lawfully use to calculate fines.

Beyond its technical legal interest, the judgment carries direct strategic implications for businesses that purchased cables from the sanctioned manufacturers during the cartel period and may have suffered overcharges. At Stonward Litigation Finance, we analyse the key aspects of this ruling and its potential impact on cartel damages claims.

Background: the enforcement action and judicial history

The case originates from a sanctioning decision issued by Spain’s National Markets and Competition Commission (CNMC) on 23 November 2017, in case file S/DC/0562/15 Cables BT/MT. The CNMC found the existence of several cartels in the low- and medium-voltage cables market, including the “manufacturers’ cartel” and the “Peisa and manufacturers’ cartel,” attributing liability to various companies including Top Cable, S.A.

The National Court (Audiencia Nacional) partially upheld Top Cable’s appeal. It ruled that the overcharge parameter used by the CNMC to quantify the fine in the manufacturers’ cartel was unsubstantiated, and annulled the sanction relating to the Peisa cartel on the basis that only three isolated episodes—separated by long time gaps—had been proven, which were insufficient to constitute a continuous infringement.

Both the State (representing the CNMC) and Top Cable filed cassation appeals before the Supreme Court.

The Supreme Court’s key rulings

1. Continuous infringement: the common plan prevails over time gaps

The Supreme Court establishes clear doctrine: where a common plan to engage in anticompetitive activity is proven, time gaps between proven infringing episodes do not, by themselves, prevent the infringement from being classified as continuous.

This has a direct impact on limitation periods. The limitation clock starts running from the end of the last proven conduct under the plan, not from each individual episode. However, the Court introduces an important safeguard: if the gap between one episode and the next exceeds the limitation period for the infringement considered individually (four years for very serious infringements), the earlier conduct must be deemed time-barred.

In this case, the gaps of three years and eight months and three years and four months between proven episodes were below the four-year threshold, so the Court upheld the continuous infringement classification and found that the National Court had erred in declaring prescription.

Nevertheless, the Court clarifies that where significant intervals of inactivity exist within a continuous infringement, the sanctionable duration cannot be treated as equivalent to an uninterrupted course of conduct. The fine must be calculated by reference to the time of proven execution, excluding periods in which no activity attributable to the plan is established.

2. Fining criteria: “conduct participation quota” lacks legal basis

The second question resolved by the Supreme Court is equally significant. The CNMC had used a parameter called the “conduct participation quota” (cuota de participación en la conducta) to graduate fines among the various sanctioned companies. This criterion, defined in the CNMC’s 2018 Provisional Guidelines, measures each company’s proportional share in the combined turnover of the investigated companies.

The Supreme Court holds that this criterion has no normative basis in Article 64(1) of the Competition Act (Ley de Defensa de la Competencia, LDC). The Court reasons that the conduct participation quota is not equivalent to market share (Art. 64.1.b LDC), does not measure the dimension and characteristics of the affected market (Art. 64.1.a LDC), and does not fit within any of the other expressly listed legal criteria.

Furthermore, the Court concludes that the open-ended clause “among others” in Article 64(1) LDC cannot be read as a blank authorisation to introduce sanctioning criteria unrelated to those established by law, as this would violate the principle of legality in sanctions under Article 25(1) of the Spanish Constitution.

Practical consequences of the judgment

As a result, the Supreme Court set aside the National Court’s judgment, partially upheld Top Cable’s original appeal, and annulled the sanctioning decision solely in relation to the determination of the fine amount, ordering the CNMC to recalculate the sanctions in accordance with the criteria set out in the judgment. The existence of the infringement, its legal classification, and the attribution of liability remain confirmed.

Implications for affected businesses and damages claims

It is important to note that this is a public enforcement judgment—not a damages ruling—but its reasoning carries strategic relevance for follow-on cartel damages claims:

• Confirmed infringement: the existence of the cartel and the participation of the sanctioned companies are now final. This provides a foundational element for assessing potential damages claims.
• Extended relevant period: by confirming the continuous infringement classification, the potentially affected period spans the full duration of the common plan, broadening the timeframe for identifying purchases subject to overcharges.
• Limits on fine calculation do not bar damages claims: the fact that the CNMC must recalculate the fine does not affect the existence of the infringement or the right of injured parties to seek compensation.

That said, the judgment does not automatically prove that every customer of the cartel suffered harm, nor does it guarantee compensation. Affected businesses need to individually analyse aspects such as the specific purchase period, the volume of relevant acquisitions, economic evidence of the overcharge, causation, and the quantification of actual loss.