The thesis will briefly cover the origin of the principle, its appearance in EU law as a general principle deriving from the rule of law and subsequent “codification” in the Treaties as a principle governing the exercise of EU’s legislative competence.

The main part of the thesis will be focused on comparing how the principle manifests itself in its application throughout different situations within EU law. Since the principle is one the general principles, it pervades through the entire acquis and hence can appear in various settings, performing a very different role in each of them, with different tests and levels of judicial scrutiny attached.

There are, in theory, three primary functions of the principle of proportionality:
1) it is used as a ground for review of EU measures;
2) it is used as a ground for review of national measures affecting one of the fundamental freedoms;
3) it governs, together with the principle of subsidiarity, the exercise of EU’s legislative competence

Supposedly, another function emerged with the EU Charter coming into force. Indeed, the principle of proportionality, when applied outside EU law, is most often connected with protection of human rights. The thesis will thus try to explore whether the application of the principle in regard to the Charter differs from the one applied in regard to restrictions on fundamental freedoms and very briefly also whether the application of the principle differs from other judicial bodies applying the principle in connection with human rights, most notably the ECtHR.

In its conclusion, the thesis will try to answer whether the principle of proportionality in EU law can be understood as one principle that is slightly modified by the field it is applied in or whether it should rather be understood as a term loosely connecting various concepts that are distinctively different and share little to no similarities except for the very basic maxim that action undertaken must be proportionate to its objectives.