The Court of Justice of the European Union is often described as a neutral engine of European integration. Yet as Silje Synnøve Lyder Hermansen, Matthew Gabel and Jay N. Krehbiel show, behind the Court’s unified voice lies a politically divided institution.
We like to talk about the Court of Justice of the European Union as if it were a machine – an “engine of European integration”. Sometimes, this machine “pushes integration”. Sometimes, it “pulls back”.
We often see debates over whether the Court is “overreaching” or why it is “showing restraint”. But the underlying image is always the same: one Court, one will, one direction. An institution that is occasionally controversial, but basically unified.
This is a useful picture. Judges do share a strong interest in protecting the Court’s authority – and, ideally, levelling the odds and spotlighting rights protections for individual litigants facing more powerful opponents along the way.
That unity is not accidental. It is part of the Court’s legalist brand, designed to shield judges from political pressure. The Court does not publish dissenting opinions. Deliberations are secret. Judgments are issued in the name of “the Court”.
And yet the Court of Justice is politically divided. Not in the way parliaments are divided, but in ways that matter for how European law is made, how long it takes and who benefits when it finally arrives. In a recent study, we draw on new data on judicial preferences to show that decisions take longer when judges sit far apart ideologically, and that timing itself can be used strategically.
What the appointment process tells us about judges
Judges are human. Like everyone else, they carry views, values and intuitions that shape how they reason about law, markets and the role of public authority.
For a long time, however, these preferences were difficult to observe. There are no votes and no public traces of disagreement in a court designed to speak with one voice. Unity was inferred from silence. Yet the way judges are appointed can offer some clues about where disagreement might emerge.
Judges are nominated to the Court by each of the EU’s member states. All 27 governments have received a democratic mandate and campaigned on policy choices about markets, regulation, redistribution and the role of the state. These commitments inevitably inform who is selected for the Court. This appointment process makes the different preferences of judges traceable.
We use the “Ideology on Both Sides” dataset (available on Harvard Dataverse) to place judges and their appointing governments in the same policy space. This makes political disagreement observable in a court that works hard to conceal it. By scaling the political parties that appoint judges from their electoral manifestos and letting judges “inherit” those preferences, we can open the black box of collective judicial decision-making.
If political disagreement matters, it should leave fingerprints in how the Court functions – not only in the ideological character of rulings but also in how long the Court deliberates, how difficult consensus becomes and where friction accumulates.
A polarised Court takes longer to make decisions
We analysed close to 20,000 judgments delivered between 1990 and 2023. The main finding is straightforward: the more polarised the Court is – the further apart judges sit ideologically – the longer it takes to decide cases.
The most consequential delays are driven by conflict over the role of government in the economy. You can see the main results depicted in Figure 1. Realistic shifts in judges’ economic left-right polarisation correspond to a 52 percent increase in decision duration, compared with 16 percent for disagreement over European integration.
Figure 1: Effect of judges’ left-right economic preferences on case duration
Note: For more information, see the authors’ recent study in European Union Politics.
To understand where these delays arise, we estimate the effect of polarisation separately across policy areas. Most delays stem from disagreement over economic governance in topics that dominate the Court’s workload: competition law, public procurement, commercial policy, cohesion spending, energy, taxation, agriculture, transport, social policy, public health and even internal staff disputes. These are distributive and regulatory fields in which judges clash over how far markets should be constrained.
When we consider preferences related to European integration, polarisation matters most in central, relatively new and highly contested areas of EU policy: environmental regulation, justice and home affairs, the freedom to provide services and questions touching the EU’s legal order. Taken together, the message is clear: the Court’s productivity has varied over time, depending on case inflow and available resources. But it also hinges on internal disagreement.
Managed disagreement
Importantly, that disagreement is harnessed. Judges supply different levels of expertise, effort and motivation, but they are also pitched against one another through internal checks and balances.
Power is delegated, but not freely. A lead judge is appointed with proposal power, but final decisions are reached by majority vote. Bargaining therefore centres on persuading pivotal judges to trade policy direction for stronger legal arguments.
Anyone willing to invest time in the process may chip in. A recent working paper shows how the Court’s interventionist stance on economic issues fluctuates with the ideological composition of the panel, with the lead judge in a particularly advantageous position.
Upstream from the final deliberations, the rest of the Court decides how closely that authority should be watched by adjusting chamber size, calling hearings or inviting competing legal opinions. This takes time and resources that are spent monitoring judges, gathering information and bargaining over both outcomes and arguments.
The result is more than bureaucratic plumbing. It is a court that governs through managed disagreement. Preferences matter, but only after they pass through layers of collective scrutiny.
Negotiating integration
None of this happens in a vacuum. External actors shape the Court’s environment at every stage. National judges, private litigants and the Commission act as gatekeepers to the Court’s agenda by deciding which disputes it hears. During proceedings, government submissions signal political stakes and potential backlash. The Court anticipates these signals. It adjusts how – and when – it speaks.
Crucially, these interactions are not one-sided. When the Court engages with governments, there is ideology on both sides: appointments mean that judicial preferences broadly follow political shifts in the member states, but never mechanically. Changes arrive slowly, unevenly and are filtered through the Court’s own internal structures.
Litigation, in this sense, is not just a legal process but a political exchange, shaped by expectations on both ends. The Court manages this exchange not only through what it decides but also through when it decides, by timing rulings to coincide with domestic political climates more receptive to European integration and compliance.
This is why understanding judges’ preferences matters. If judges bring systematic views about markets, regulation and public authority to the bench, judicial politics is not only about how cases are decided but also about which kinds of litigation the Court invites, how it responds to political signals and which battles it chooses to fight or avoid.
The Court still speaks with one voice. But that voice is forged through managed disagreement. Integration is not driven by a machine. It is negotiated – carefully, collectively and often slowly – inside a politically divided court.
For more information, see the authors’ recent study in European Union Politics.
Note: This article gives the views of the authors, not the position of LSE European Politics or the London School of Economics.
Image credit: olrat provided by Shutterstock.
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