CJEU review puts EU–Mercosur deal on constitutional hold

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January 23, 2026

© Abhishek Tewari /Unsplash(Chess pieces arranged on a board. A vintage wooden chess figure, illustrating the CJEU, being used by the EP to delay the Mercosur Agreement, even to avoid it against political competitors.)

The Court of Justice of the European Union (CJEU) is set to weigh in on the EU–Mercosur Agreement after the European Parliament requested an advisory opinion under Article 218(11) TFEU on the agreement’s compatibility with EU primary law. The move shifts the center of gravity of the ratification debate from political bargaining to constitutional adjudication, with direct consequences for the agreement’s legal trajectory.

Under Article 218(11) TFEU, EU institutions may seek an ex ante ruling on whether an international agreement complies with the Treaties. If the Court were to find incompatibility, the agreement could not enter into force in its current form. Even in the absence of such a finding, the procedure introduces a significant temporal delay, as the Court’s opinion is not expected before late 2026 at the earliest.

Crucially, however, a pending CJEU opinion does not automatically preclude provisional application of the agreement’s trade components. Provisional application, decided by the Council and not subject to parliamentary consent, has long been used to bridge extended ratification periods. The EU–Canada CETA provides a relevant precedent: it has been provisionally applied since 2017, despite still not having formally entered into force.

From a legal perspective, existing CJEU case law offers mixed but not unfavorable signals. In Opinion 1/17, the Court upheld CETA’s compatibility with EU law, including its controversial investment court system, an element absent from the EU–Mercosur Agreement. Earlier, in Opinion 2/15 on the EU–Singapore agreement, the Court broadly confirmed the scope of the EU’s exclusive competence in trade policy, reinforcing institutional discretion in external economic relations.

Beyond the substance of the Mercosur deal, the referral underscores a broader pattern. The CJEU is increasingly acting as an arbiter not only of legal boundaries, but of political timing. In EU trade policy, judicial review is no longer merely a safeguard of constitutionality, it has become a strategic variable in managing contested external commitments.

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