The starting point
The European Union can change only through law. The central route is Article 48 of the Treaty on European Union, which sets ordinary and simplified procedures for treaty revision. A proposal can come from a national government, the European Parliament, or the Commission.
Under the ordinary revision procedure, the European Council can decide to examine proposed changes. A convention may then bring together representatives of national parliaments, governments, the European Parliament, and the Commission. Its recommendations go to an intergovernmental conference, where governments agree the final amendments.
How this works in practice
Treaty amendments enter into force only after ratification by every member state according to its constitutional requirements. That can mean parliamentary approval, a referendum, or both. This high threshold protects consent, but it also makes comprehensive reform difficult.
A genuine federal settlement would need more than changing a few voting rules. It would have to define European and national powers, strengthen parliamentary control, clarify the executive, protect fundamental rights, preserve subsidiarity, and create a fair amendment process for the future.
What this means for a shared Europe
There are also political choices about membership. If not every current member wanted to join a federation at the same time, Europe would need lawful arrangements that protect the single market, citizens' rights, and cooperation without allowing permanent ambiguity to paralyse those ready to integrate further.
The democratic standard matters as much as the legal route. Citizens should see competing constitutional proposals, independent analysis, public debates, national and European parliamentary scrutiny, and a clear final choice. Federal Europe should be built in daylight.