The Mercosur deal: from theory to practice

Thursday 19 March 2026

The EU–Mercosur agreement has now entered a new and decisive phase. What, only weeks ago, appeared to be a controversial but incomplete political manoeuvre has, as of 17 March 2026, become something closer to a geopolitical fact. With Paraguay’s ratification, the last procedural barrier on the South American side has fallen, transforming the agreement from a contested diplomatic project into a structure poised for real-world operation.

This development alters not only the legal and institutional landscape of the agreement, but also its political meaning.

The agreement now fully ratified in Mercosur

The central update is simple, but profound. Paraguay has now become the final Mercosur state to ratify the agreement, completing the bloc’s internal approval process after Argentina, Brazil and Uruguay had already done so. 

The Paraguayan Chamber of Deputies approved the agreement unanimously, following Senate endorsement, leaving only the formal signature of President Santiago Peña to complete the national procedure. 

This step is not merely symbolic. Ratification by all founding Mercosur members was a necessary precondition for the agreement to move forward towards implementation. 

Accordingly the EU–Mercosur agreement now stands in a peculiar constitutional position:

• Fully ratified on the Mercosur side

• Signed and politically endorsed within the European Union

• Subject to legal review and incomplete ratification within the EU

This asymmetry is the defining feature of the present moment.

From political project to operational reality

The Commission’s earlier decision to pursue provisional application now takes on concrete significance. When Ursula von der Leyen announced that the EU would move towards provisional enforcement of the trade pillar, the decision was framed as anticipatory—contingent upon Mercosur’s internal processes reaching completion.

That condition has now been met.

The agreement therefore transitions from theoretical controversy to imminent economic instrument. It is expected to begin provisional operation in the first half of 2026, potentially within weeks, depending on the exchange of formal notifications between the parties. 

In practical terms, this means that tariff reductions and market access provisions could begin to affect trade flows even while the European Parliament continues its legal and political deliberations.

The agreement thus becomes one of those rare creatures in European law: a treaty that exists simultaneously in force, in dispute and in flux.

Reframing the controversy

Paraguay’s ratification does not diminish the controversy surrounding the agreement; rather, it sharpens it.

Previously opponents could argue that the agreement remained hypothetical or reversible. Now, with the South American side unified, the argument shifts. The question is no longer whether the agreement should exist, but whether Europe can afford to resist its implementation.

Farmers and distributional politics

The agricultural critique remains unchanged in substance but altered in urgency. European farmers—particularly in France, Ireland and Poland—are no longer protesting a potential future influx of South American agricultural goods. They are confronting a process already in motion.

The political psychology of this shift is important. Opposition hardens when a policy appears inevitable.

Environmental legitimacy

Likewise, environmental objections—centred on deforestation and sustainability—now attach themselves to an agreement that is effectively advancing regardless of those concerns. This raises a deeper question about European governance: whether sustainability clauses in trade agreements meaningfully constrain outcomes, or merely legitimise them.

Institutional legitimacy

Most acute of all is the constitutional objection.

The European Parliament has already referred key questions about the agreement’s legality to the Court of Justice of the European Union. The concern is that the Commission’s strategy—splitting the agreement into components and proceeding with provisional application—may bypass the full democratic scrutiny ordinarily associated with mixed agreements.

With Mercosur ratification complete, that legal question becomes more urgent rather than less. If the Court ultimately finds fault with the procedure, the EU could find itself partially implementing an agreement whose legal foundations are contested.

The legal battles ahead

The core legal issues remain as previously identified, but Paraguay’s ratification increases their stakes.

First, there is the question of competence and procedure: whether the EU can legitimately provisionally apply large parts of the agreement without full ratification by member states and Parliament.

Second, there is the issue of regulatory autonomy: whether mechanisms within the agreement constrain the EU’s ability to set environmental, health and agricultural standards without triggering retaliation.

Third, there is the practical problem of reversibility. If the European Parliament ultimately rejects the agreement, provisional application must be unwound—a process that is legally complex and politically costly.

The more the agreement begins to operate in practice, the harder such unwinding becomes.

Geopolitical consequences in light of Paraguay’s ratification

With all Mercosur states aligned, the geopolitical meaning of the agreement becomes clearer.

A completed Atlantic axis

The EU has, in effect, secured a comprehensive economic relationship with a bloc representing over 700 million people and a substantial share of global GDP. 

This creates a transatlantic economic axis that sits alongside, and partly in competition with, existing global trade structures.

For Europe, this is an assertion of strategic autonomy—diversifying supply chains and export markets at a time when both the United States and China are increasingly willing to use trade relationships as weapons of economic warfare.

South America’s strategic hedging

For Mercosur, full ratification signals a deliberate diversification of external partnerships. The bloc deepens its ties with Europe without abandoning its extensive economic relationships with China or its proximity to the United States.

Paraguay’s ratification is therefore not merely administrative; it is a statement of regional consensus in favour of outward-looking economic integration.

Pressure on EU internal cohesion

Yet the asymmetry between Mercosur unity and European division is striking.

South America has completed its part of the bargain. Europe has not.

This imbalance increases pressure on the EU’s internal political system. Member states and Parliament must now decide whether to align with a process already endorsed by their counterparts, or to resist it at the cost of diplomatic friction and economic opportunity.

A treaty in motion

The EU–Mercosur agreement now occupies a rare and unstable category. It is:

• Negotiated over a quarter century

• Signed and politically endorsed

• Fully ratified by one side

• Partially implemented

• Legally contested

• Politically divisive

Paraguay’s ratification does not resolve these contradictions. It crystallises them.

What had been a slow-moving diplomatic exercise has become an immediate test of European governance—of how it balances law and expediency, democracy and strategy, internal consent and external necessity.

The agreement is no longer a future possibility. It is an unfolding reality. And the question that now confronts Europe is not whether it can negotiate such agreements, but whether it can live with the consequences of having concluded them.