This provision places sustainable development at the core of the EU’s internal goals. It reiterates the economic, social, and environmental progress interdependence, thus reinforcing sustainability as a tripartite principle. Moreover, it brings in “high level of environmental protection” as guiding principle which embeds environmental quality as a fundamental concern in the functioning of the internal market and all policies of the Union. The CJEU has been instrumental in enforcing these treaty obligations and clarifying their legal boundaries. In Commission v Austria (C-28/09), the Court considered Austria’s environmental justification for restricting transit traffic through the Tyrol region.1 The Austrian measure was considered w disproportionate to the EU market law, although the court accepted environmental protection as a legitimate objective. This case demonstrates the careful judicial balance between economic freedoms and environmental objectives as required by Article 3(3) TEU.

The TEU’s external dimension (Article 3(5)) connects the EU’s sustainability ethos to global justice and planetary care in a post-national constitutional ethic. This paragraph extends the EUs sustainability commitment to the area of its external action, making the EU a global actor for sustainable development, climate leadership and environmental justice. It creates a normative framework to mainstream sustainability in EU trade policy, international development cooperation and climate diplomacy. In Air Transport Association of America v Secretary of State for Energy and Climate Change (C-366/10) the Court rejected the AG´s opinion and erased the GHG Emissions Trading System (abbr. ETS) as applied to extra-European aerospace.2 This judgment reinforced the EU’s authority to regulate environmental impacts with extraterritorial dimensions, underscoring the external sustainability commitment in Article 3(5) TEU.

Article 3 TEU aligns with SDG 8: Decent Work and Economic Growth, SDG 11: Sustainable Cities and Communities, SDG 12: Responsible Consumption and Production, SDG 13: Climate Action, SDG 17: Partnerships for the Goals, SDG 16: Peace, Justice and Strong Institutions.

The described legal frameworks envision long-term sustainable development, particularly by Article 3(3) requiring the Union to pursue strong environmental protection alongside social advancement in relation to the internal market. Additionally, Article 3(5) extends this normative obligation to the Union’s external action, stating that the Union must aid global sustainable development, environmental protection, and the eradication of poverty. There is no denying the symbolic importance of these provisions; now, sustainability sits at the constitutional heart of the European project. However, their legal impact is limited by the nature of their aspirational governance. They lack concrete obligations that are legally binding or justiciable, rendering them largely ineffectual in litigation or legislative review. The loose terminology, “shall work for,” provides minimal enforcement capabilities which relies heavily on collective will from the Member States and institutions. In addition, while a commitment to global sustainability is made in Article 3(5), the EU tends to impose lower environmental protection standards in its external trade, agriculture, and investment policies than those it upholds internally, exposing a normative gap between treaty-based ambition and geopolitical practice. Unlike some federal constitutions (e.g., Germany or the US), the TEU does not establish an enforceable institutional or procedural infrastructure for evaluating sustainability across EU law.