The principle of proportionality is a political maxim which states that any layer of government should not take any action that exceeds that which is necessary to achieve the objective of government. It was initially developed in the German legal system.

It is a fundamental principle of European Union law. According to this principle, the EU may only act to exactly the extent that is needed to achieve its objectives, and no further. This principle has underpinned the European Union since its inception in 1957. It is explicitly specified in the proposed new Treaty establishing a constitution for Europe. In the presently applicable primary law, this principle is clearly formulated in the third paragraph of Article 5 of the Treaty establishing the European Community as follows: European Union law is the unique legal system which operates alongside the laws of Member States of the European Union (EU). ... 1957 (MCMLVII) was a common year starting on Tuesday of the Gregorian calendar. ... The constitutional treaty as signed in Rome on 29 October 2004 by representatives of the EU member states The Treaty establishing a Constitution for Europe (TECE), commonly referred to as the European Constitution, was an international treaty intended to create a new constitution for the European Union. ... The Treaty of Rome signing ceremony Signatures in the Treaty The Treaty of Rome, signed by France, West Germany, Italy and Benelux (Belgium, the Netherlands and Luxembourg) on March 25, 1957, established the European Economic Community (EEC). ...

Any action by the Community shall not go beyond what is necessary to achieve the objectives of this Treaty.