This document is an excerpt from the EUR-Lex website
Article 223 of the Treaty on the Functioning of the European Union requires the European Parliament (EP) to propose provisions necessary for the election of its members by direct universal suffrage in accordance with a uniform procedure in all EU countries or in accordance with principles common to all the countries. The necessary provisions are laid down by the Council, andenter into force after approval by the EU countries.
Council Decision 2002/772/EC, Euratom introduced the principles of proportional representation (using a list or a single transferable vote) and incompatibility between national and European mandates (for example, a Member of the European Parliament may not be a member of government of an EU country). This decision still governs the procedure given the difficulty of reaching agreement on the harmonisation of national traditions.
The right to vote and stand as a candidate is a fundamental right under Article 39 of the EU's Charter of Fundamental Rights. Article 22(2) allows EU nationals residing in another EU country to vote and stand for election in EP elections (unless they have been subject to an individual judicial or administrative decision to the contrary).
National rules cover aspects such as seat allocations, constituency boundaries, voting age, election dates and the nominations process.