This article is an opinion piece by current students or alumni of the College of Europe. The views expressed are those of the authors and do not necessarily reflect the opinions or positions of the College of Europe. Responsibility for the content lies solely with the authors.
By Elia Kostopoulou
In this interview, Antonio Bavasso, Global Co-Chair of the Antitrust and Trade Regulation Practice at Simpson Thacher & Bartlett LLP, and Henry Llewellyn, competition and regulatory lawyer at Simpson Thacher & Bartlett LLP, discuss the evolving landscape of EU merger control and cross-border regulatory enforcement, including the European Commission’s ongoing review of the EU Merger Guidelines, the increasing importance of innovation and ecosystem theories of harm, and the growing interaction between merger control, foreign direct investment screening, and the Foreign Subsidies Regulation. The conversation further explores the practical realities of managing global multi-jurisdictional transactions, the role of internal documents and economic evidence in merger investigations, the challenges of designing remedies across jurisdictions, and the broader shift toward more interventionist enforcement in digital and technology markets, offering insight into how competition authorities currently approach complex strategic acquisitions in an increasingly interconnected regulatory environment.
Question One: The Commission is formally reviewing the EU Merger Guidelines (1). What is one change you would genuinely welcome because it would increase predictability for deal teams, and one change you would be more cautious about, for fear that it could institutionalise excessive discretion? What parts of EU merger control are currently too unpredictable, and where would you draw the line between helpful clarification and giving the Commission too much freedom to block deals?
Answer: EU merger control under the Council Regulation (EC) No 139/2004 (the “ EUMR ”) cannot be described as structurally unpredictable. It has been shaped through extensive decisional practice and judicial review under the significant impediment to effective competition (“SIEC”) test, and in conventional horizontal cases a relatively stable analytical framework has been established. The areas in which uncertainty is most acutely perceived are not foundational elements of the system, but rather those involving forward-looking or theory-driven assessments.
One change that would genuinely be welcomed concerns greater clarification of innovation theories of harm. Innovation effects are necessarily assessed through probabilistic and counterfactual reasoning, and future R&D trajectories are evaluated under conditions of uncertainty. In such contexts, the evidentiary threshold has not always been clearly articulated. More detailed guidance could be provided as to what type of internal documentation, economic modelling, or pipeline evidence is regarded as sufficient to establish a credible innovation overlap, how the relevant counterfactual is to be constructed, and how merger-specific reductions in innovation incentives are to be distinguished from general market uncertainty. By strengthening methodological discipline in this way, predictability would be enhanced without the substantive legal standard being lowered.
Clarification would also be beneficial in relation to ecosystem and conglomerate theories of harm, particularly in digital markets. In such cases, competitive harm is often inferred through leveraging mechanisms involving tying, bundling, defaults, data advantages, or interoperability constraints. Greater predictability would be achieved if it were more clearly specified that market power at an “anchor” level must first be demonstrated, that a technically and economically plausible leveraging mechanism must be established, and that a foreclosure pathway capable of producing measurable competitive harm must be substantiated. Where these causal links are not rigorously required as part of the standard of proof, there is a risk that efficiency-enhancing integration may be characterised as exclusionary strategy without sufficient evidentiary grounding.
Greater caution would, however, be warranted if reforms were to introduce broader structural presumptions or more open-ended discretion in dynamic or digital markets. The SIEC test was designed as an effects-based standard grounded in economic analysis. If intervention were to be facilitated through ambiguous concepts, lowered evidentiary demands, or expansive presumptions concerning innovation spaces, data accumulation, or ecosystem positioning, the balance between enforcement effectiveness and legal certainty could be destabilised. In such circumstances, merger control might gradually be transformed into a policy instrument of industrial regulation rather than a disciplined assessment of competitive effects.
A further source of unpredictability lies in the treatment of efficiencies. Although efficiencies are formally recognised within the EU framework, they are often perceived as difficult to rely upon in practice unless they are exceptionally concrete, merger-specific, and verifiable within a relatively short timeframe. More transparent articulation of the standard of proof required and of the manner in which efficiencies are weighed against potential dynamic harms would enhance credibility and symmetry in the assessment.
The line should therefore be drawn between clarification that improves methodological consistency and reforms that effectively expand interventionist discretion. Where evidentiary standards are clarified, analytical steps are structured, and counterfactual reasoning is disciplined, legal certainty is strengthened. Where concepts are broadened without corresponding safeguards, discretion is institutionalised. The objective of the revised Guidelines should not be to make it easier for transactions to be prohibited, but rather to ensure that both prohibitions and clearances are grounded in transparent, consistently applied reasoning.
Question Two: In your experience, what is the earliest piece of evidence that genuinely moves the needle with regulators today: internal strategy documents, customer switching data, pricing or auction datasets, or economic modelling, and why? When regulators start reviewing a deal, what type of evidence shapes their view first and most decisively?
Answer: At the earliest stage of review under the EUMR, it is typically internal strategy documents that shape the direction of the case most decisively. This is not accidental. Both practically and conceptually, such material performs a distinctive function in merger analysis.
From a practical perspective, internal documents provide an immediate and unfiltered window into how the business itself understands the competitive landscape. They reveal which competitors are regarded as close constraints, where expansion threats are perceived, how pricing or innovation strategies are framed internally, and what strategic rationale is driving the transaction. At a moment when regulators are forming their initial theory of harm, this material is often reviewed before complex datasets have been processed or econometric exercises have been completed. As a result, it frequently anchors the preliminary narrative of the case.
From a theoretical perspective, modern merger control is fundamentally incentive-based. Under the SIEC framework, the central question is whether competitive incentives are altered in a manner that significantly impedes effective competition. Internal documents speak directly to incentives. They may reveal whether a rival is viewed as particularly disruptive, whether competitive pressure is felt intensely in specific segments, or whether the transaction is expected internally to soften rivalry or reshape strategic positioning. Such insight cannot be replicated at the same early stage by raw pricing data or switching statistics, which require interpretation and modelling before their implications can be understood.
This dynamic is reinforced by the way merger assessment is operationalised in practice. Considerable attention continues to be devoted to market definition and market shares, even in differentiated, multi-sided, bidding, or rapidly evolving markets where competitive constraints are more fluid. In such settings, formal market share exercises may risk becoming artificial or incomplete. Internal documents often cut through that formalism by revealing how substitution patterns and competitive constraints are perceived in the ordinary course of business, rather than reconstructed ex post for notification purposes.
Quantitative evidence, such as customer switching data, auction outcomes, pricing datasets, or economic modelling, remains critically important. However, it is often deployed to test, refine, or corroborate an initial theory of harm that has already been influenced by documentary evidence. By the time econometric modelling is conducted, the analytical frame may already have been shaped by how the parties themselves described competition and strategic intent.
For that reason, the earliest evidence that moves the needle is usually the evidence that reveals incentives most directly. Internal strategy material performs that function in a uniquely immediate way, and it is therefore often decisive in setting the trajectory of regulatory scrutiny.
Question Three: As a firm, you have acted on precedent-setting TMT clearances and regulatory litigation. Where do you see the Commission (and the EU courts) currently drawing the line between a legitimate ‘ecosystem strategy’ and conduct that becomes legally vulnerable, particularly when the analysis turns on defaults, data advantages, or interoperability? When does integration stop being normal strategy and start being exclusion?
The line that is currently being drawn is most defensibly described in functional terms rather than as a bright rule. Ecosystem strategies are generally treated as legitimate when they reflect competition on the merits such as product improvements and integration efficiencies, even where aggressive commercial design choices are being made. Legal vulnerability is more likely to be found where integration is pursued by an undertaking with entrenched market power and where the architecture of the ecosystem is credibly capable of protecting, extending, or entrenching that power through foreclosure. In other words, integration is not treated as the core problem; integration, combined with durable power and a plausible exclusionary pathway that goes beyond competition on the merits, is.
In the Commission’s approach, the assessment tends to be structured implicitly around a sequence of questions. The starting point is the degree and durability of market power, including whether the relevant position is protected by entry barriers such as scale, network effects, default bias, switching costs, or control over a bottleneck interface such as an operating system. The next step is the mechanism through which ecosystem design is alleged to operate. Defaults, data advantages, tying or bundling, and interoperability choices are examined not as abstract features, but as tools that may be used to raise rivals’ costs, restrict access, or weaken rival distribution channels. The final step is effects, with particular focus being placed on whether competitive constraints are likely to be weakened in a manner that is durable, self-reinforcing, and difficult to reverse in markets characterised by feedback loops between usage, data accumulation, and quality improvements.
The legal discipline that has to be preserved in this area is causation and counterfactual reasoning. A competitive disadvantage experienced by rivals is not, by itself, unlawful; it may simply be the natural outcome of competition on the merits, such as a superior product, better integration, or more attractive user experience. The critical question is whether rivals are being displaced because competition is being won on the merits, or because the ecosystem architecture makes effective rivalry irrational or practically impossible even for equally efficient non-dominant competitors. This is where defaults and interoperability become particularly sensitive. Default settings may be competitively benign where they reflect genuine consumer preference or product quality, but concern is more likely to crystallise where default bias is exploited to steer users systematically and where realistic avenues for switching or multi-homing are being materially impeded. Similarly, interoperability limitations may be justified where security, privacy, integrity, or engineering constraints are credibly demonstrated, yet legal risk becomes more acute where a controlled interface functions as a bottleneck and pathways that previously enabled rivalry are closed without persuasive technical necessity.
Judicial review then operates as the constraint mechanism that prevents “ecosystem” from becoming an empty label. When novel theories of harm are advanced, the Commission’s reasoning is expected to be supported by coherent evidence and by an economically plausible narrative showing that the anticompetitive scenario is not merely conceivable but sufficiently likely. By applying that standard, the EU courts contribute to ensuring that integration is not treated as presumptively suspicious, and that intervention is not warranted unless a robust causal chain between the conduct and the alleged exclusionary effects is demonstrated. The practical consequence is that integration tends to stop being seen as normal strategy, and to start being characterised as exclusion, at the point where durable market power is combined with design choices that materially foreclose equally efficient rivals and where persistent harm to competitive constraints is credibly substantiated.
Question Four: Given your leading combined European antitrust and foreign investment practice, when a transaction triggers both merger control and foreign-investment or foreign-subsidy scrutiny, what sequencing strategy best minimises execution risk (parallel filings, staged sign-and-close mechanics, or ring-fencing)? What trade-off do clients most often underestimate?
Answer: In most significant transactions today, parallel processing of the filings has effectively become the default approach. Under the EUMR, merger control review is designed to assess whether a concentration would significantly impede effective competition. By contrast, Foreign Direct Investment (“FDI”) screening regimes focus on national security or public order concerns, and review under the Foreign Subsidies Regulation (“FSR”) examines whether a transaction has been facilitated by distortive foreign state support. Because these frameworks pursue fundamentally different objectives, sequencing is no longer a purely competition-law question; it has evolved into a broader cross-regime project management exercise.
Parallel filings are often pursued in order to advance the transaction clock as efficiently as possible. However, the principal risk is not merely one of timing but of conceptual misalignment. Each regime is guided by distinct policy priorities, evidentiary thresholds, and political sensitivities. Even where coordination between competition authorities has improved — frequently facilitated through waivers and informal engagement — FDI processes may remain less predictable, more nationally contextual, and more exposed to geopolitical considerations. Review under the FSR adds a further layer of complexity, as information requests can be expansive and resource-intensive, and the assessment may extend beyond traditional competition metrics.
A common trade-off that tends to be underestimated is that accelerating all regimes simultaneously can increase procedural friction. Divergent confidentiality constraints, differing disclosure obligations, and inconsistent approaches to remedies can generate tension across filings. A position adopted in one regime may be scrutinised differently in another, particularly where the characterisation of strategic assets, state influence, or market positioning carries different legal consequences.
For that reason, effective sequencing is often less about rigid ordering and more about preserving structural optionality within the transaction documentation. Conditions precedent are carefully calibrated, long-stop dates are drafted with realistic regulatory timelines in mind, interim covenants are framed to allow operational flexibility, and contingency planning is undertaken for potential remedies or behavioural commitments that may arise in one regime but not in others. The practical objective is to align the overall timetable with the slowest and least predictable approval process, without allowing that regime to dictate the entire transaction strategy.
Execution risk in multi-regime deals is therefore shaped less by pure antitrust analysis and more by coordination, narrative consistency, and disciplined expectation management across regulatory silos.
Question Five: Much of your recent work has involved cross-border, private-equity-driven transactions. When multiple authorities are involved and their competitive concerns are not fully aligned, how do you approach building a single, coherent remedies story that works across jurisdictions? At what point do you start thinking seriously about remedies, before Phase II risk becomes clear?
Answer: The central principle is that remedies cannot be designed in isolated national silos where the transaction itself is global in scope. Even if substantive concerns are expected to crystallise in only one jurisdiction, any remedy, particularly a structural divestiture, may generate operational, financial, and competitive consequences across other markets. For that reason, what is required is not a locally optimised solution, but a coherent remedy strategy that is conceptually consistent, practically implementable, and credible before multiple authorities simultaneously.
The governing logic is one of proportionality and effectiveness. A remedy must directly address the specific theory of harm that has been identified, must go no further than necessary to remove the competitive concern, and must credibly restore the constraint that would otherwise be lost as a result of the transaction. Where horizontal overlaps are clear and durable, structural remedies are often favoured because an independent competitive force can be re-created. However, such remedies will only be accepted where a viable business package can be carved out, a credible purchaser can be identified, and transitional arrangements can be structured in a manner that preserves competitiveness post-divestiture.
Behavioural remedies may be regarded as more appropriate in vertical or digital contexts, particularly where concerns relate to access, interoperability, data use, or discriminatory conduct. Yet such commitments frequently raise issues of enforceability and long-term monitoring. Where ongoing access obligations, data-sharing mechanisms, or interface commitments are required, supervisory complexity increases, and authorities may scrutinise whether the remedy will remain effective over time without continuous regulatory intervention.
The timing of serious remedy planning depends on the degree to which the competition issue is already well understood. Where the overlap is obvious, the relevant market structure is stable, and a well-trodden remedy template exists, early engagement can be strategically advantageous. In such cases, disciplined pre-notification dialogue and readiness to propose a proportionate fix may reduce the risk of escalation or a protracted in-depth investigation. By contrast, where concerns are novel, theory-driven, or dependent on contested economic analysis, remedies may need to be developed dynamically. In those circumstances, it may only become clear at a later procedural stage which theory of harm is being prioritised and what type of intervention would be regarded as sufficient.
The most effective early remedy mindset is therefore not one of premature concession, but of structured preparedness. The transaction architecture, carve-out feasibility, purchaser universe, and operational separability are analysed internally from an early stage, even if no formal proposal is tabled. It is often this readiness — the ability to respond swiftly and credibly if the case crystallises in a particular direction — that prevents procedural drift and mitigates execution risk in complex, multi-jurisdictional transactions.
Question Six: You regularly handle transactions requiring clearance in Europe, the United States, and multiple national regimes. Where do you currently see the most significant practical frictions emerging between authorities, and how does this affect the way you prepare for and manage an investigation?
Answer: In practice, the most significant frictions between authorities today do not arise from fundamentally different legal standards, but rather from differences in analytical focus, procedural expectations, and evidentiary priorities. While regimes such as the EUMR and US merger control share common economic underpinnings, authorities are increasingly diverging in how they prioritise and develop theories of harm. The Commission, for instance, has shown a growing willingness to engage with innovation effects and ecosystem dynamics, whereas US agencies may, depending on the policy cycle, place relatively greater emphasis on structural indicators or more traditional competitive constraints. These are not irreconcilable differences, but they create tension in how a transaction is framed and assessed across jurisdictions.
At the same time, procedural frictions remain highly relevant in practice. The European system continues to be comparatively formalistic, with a strong emphasis on market definition and structured notification requirements, whereas other jurisdictions can adopt a more flexible, effects-driven approach earlier in the process. This means that parties are often required to construct detailed market frameworks in Europe that do not necessarily map neatly onto how the same transaction is analysed elsewhere. In contrast, in US merger investigations involving products or services that are open to interpretation on market definition, rather than calculate numerous sets of market shares across multiple candidate markets or focus on aligning on a brightline market definition, the US agencies will instead focus on the practical closeness of competition between the parties and the potential effect on pricing. In parallel, there is increasing divergence in the types of evidence that carry decisive weight. Authorities—particularly in Europe—are placing growing emphasis on internal documents as a primary lens through which they understand a transaction, but the relative importance of such evidence compared to quantitative data can vary across regimes.
These frictions have a direct impact on how investigations are prepared and managed. The approach increasingly requires a multi-layered strategy, where the case theory must be robust enough to withstand different analytical lenses simultaneously, while remaining internally consistent across filings. Internal documents receive special focus, as they are frequently examined in multiple jurisdictions and have the potential to influence the narrative from the very beginning. There is also a greater need to anticipate, at an early stage, which authorities are likely to be more interventionist on specific issues, such as ecosystems or innovation, and to calibrate engagement accordingly. In addition, there may be divergence across jurisdictions on the types of remedies that are considered acceptable to resolve competitive harm. For example, while the current US administration has shown a willingness to accept divestitures and other structural fixes, it has still not shown much renewed openness to behavioural fixes. Ultimately, the challenge is not so much aligning different legal rules, but navigating different enforcement cultures applied to broadly similar frameworks.
(1) This conversation took place on 11 February 2026. The European Commission published the draft revised Guidelines on 30 April 2026. See https://www.stblaw.com/about-us/publications/view/2026/05/01/the-draft-revised-eu-merger-control-guidelines-evolution-not-revolution-for-european-competitiveness for further information pertaining to these Guidelines.
Antonio BAVASSO
Antonio Bavasso is a leading competition lawyer and the Global Co-Chair of the Antitrust and Trade Regulation Practice at Simpson Thacher & Bartlett LLP, where he also leads the firm’s European antitrust and foreign investment group. He specialises in merger control, antitrust investigations, litigation, and strategic competition counselling, with particular expertise in the technology, media, and telecommunications sectors.
Widely recognised by Chambers and Legal 500 as a leading practitioner in competition law, he has advised on numerous precedent-setting transactions and has extensive experience before the UK Competition Appeal Tribunal, the Court of Appeal, and the EU General Court.
Henry LLEWELLYN
Henry Llewellyn is a competition and regulatory lawyer at Simpson Thacher, specialising in complex cross-border merger control, foreign direct investment (FDI), and EU Foreign Subsidies Regulation matters. Based in Brussels, he advises on high-profile global transactions before the European Commission, the UK Competition and Markets Authority, the U.S. Federal Trade Commission, and other international competition authorities.
He holds a BA (Hons) from Trinity College Dublin and a Postgraduate Diploma in European Competition Law from King’s College London, and is admitted to practice in both Belgium and England & Wales.
Evangelia KOSTOPOULOU
Evangelia Kostopoulou is an LL.M. candidate in European Legal Studies at the College of Europe. She holds a Master's degree in law and technology from Tilburg University and is admitted to the Greek Bar. She previously trained at EY Law, one of the largest national law firms in Greece.
Her academic interests lie in EU Competition Law, and she is particularly interested in questions of consumer protection, sustainability transitions and digital platform governance. Alongside these substantive concerns, she has a strong interest in competition procedure and the procedural safeguards that structure EU antitrust enforcement.
She currently serves as a Board Member of the Competition Society at the College of Europe.
