The Committee of the Regions was set up by the Maastricht Treaty in 1992, alongside another provision that gave regional ministers the right to sit in the Council of the EU on behalf of their member state. Both changes were responses to a quiet revolt by Germany's Länder, who had watched powers they exercised at home flow to Brussels with no compensating regional voice. The first plenary session was held in March 1994. The Amsterdam Treaty in 1997 expanded the Committee's remit to about two-thirds of EU legislative proposals. The Nice Treaty in 2001 capped membership at 350 and required that members be elected officials or politically accountable to elected assemblies, not appointed civil servants. The Lisbon Treaty in 2009 gave the Committee something genuinely new: the right to take cases to the European Court of Justice when EU legislation violates the principle of subsidiarity, the rule that the EU should not do what national, regional, or local government can do better.

After Brexit removed the 24 UK members in 2020, the Committee settled at 329 full members and the same number of alternates. The numbers per country reflect population, but very loosely: Malta sends members representing roughly 88,000 citizens each, Germany's send members representing 3.45 million. The work is organised into six thematic commissions, each one a kind of standing committee with its own staff and opinion-drafting machinery. CIVEX handles citizenship and external affairs. COTER handles territorial cohesion, which in practice means EU regional funding. ECON handles economic policy. ENVE handles environment, climate, and energy. NAT handles agriculture and natural resources. SEDEC handles social policy, education, employment, culture, and research. Each commission has around 100 members; each member can serve on two. They meet, they argue, they appoint rapporteurs to draft opinions. The opinions then go to plenary for adoption six times a year.

The Committee of the Regions does not legislate. It produces opinions. The European Commission, the Council, and the Parliament are legally required to consult it on proposals with regional or local impact. The Committee can also issue own-initiative opinions, putting topics on the agenda that the bigger institutions might prefer to ignore. Once an opinion is adopted in plenary, it is published in the Official Journal of the European Union and lands on the desks of every relevant EU policymaker. It is, by design, soft power. The Committee can argue, persuade, embarrass, and occasionally litigate. It cannot vote a law down. Critics call this institutional weakness. Defenders call it the only honest way to give regional government a seat at a table where the chairs belong to national capitals.

In 2020, the Committee was hauled before the European Parliament over the case of Robert McCoy, a former internal auditor who had spent two decades pursuing fraud and embezzlement allegations inside the institution. McCoy told MEPs that the Committee had run 'a vindictive campaign' against him after he blew the whistle, denigrating his personal and professional reputation. Dutch MEP Sophie in 't Veld, who had once worked at the Committee herself, called the administration 'totally incompetent and rotten to the core' and suggested budgetary sanctions. Czech MEP Tomáš Zdechovský compared the case to the film Groundhog Day, in which the protagonist is trapped in an endless time loop. For an institution premised on bringing decision-making closer to citizens, the McCoy saga was a damaging mirror: the Committee was being shown, in public, exhibiting the same opacity and self-protection it accused larger bureaucracies of.

Once a year, the Committee transforms its building into the centre of a sprawling four-day event called the European Week of Regions and Cities. Thousands of mayors, regional officials, academics, civil society representatives, and businesspeople come to Brussels to compare notes on everything from cohesion-fund spending to climate adaptation to the integration of refugees. The seminars and side events fan out across the European Quarter. It is the one week each year when the Committee's basic argument, that the people who actually deliver public services across Europe deserve a structured voice in the laws that shape that delivery, is hard to dispute. The plenary halls, normally quiet between the six annual sessions, fill with discussions in two dozen languages. Then everyone goes home to run their cities.