A case on proportionality relating to the European Union (and not the European Convention on Human Rights). The review of proportionality is very detailed and only part of it is included here.

Lord Reed and Lord Toulson said,

Proportionality in EU law

23. It appears from the present case, and some other cases, that it might be helpful to lower courts if this court were to attempt to clarify the principle of proportionality as it applies in EU law. That is the aim of the following summary. It should however be said at the outset that the only authoritative interpreter of that principle is the Court of Justice…. It has also to be said that any attempt to identify general principles risks conveying the impression that the court’s approach is less nuanced and fact-sensitive than is actually the case. As in the case of other principles of public law, the way in which the principle of proportionality is applied in EU law depends to a significant extent on the context. This summary will… demonstrate the different ways in which the principle of proportionality is applied in different contexts…

24. Proportionality is a general principle of EU law. It is enshrined in article 5(4)EU of the Treaty on European Union (“TEU”):
“Under the principle of proportionality, the content and form of Union action shall not exceed what is necessary to achieve the objectives of the Treaties.”
It is also reflected elsewhere in the EU treaties, for example in article 3(6)EU :
“The Union shall pursue its objectives by appropriate means commensurate with the competences which are conferred on it in the Treaties.” The principle has however been primarily and most fully developed by the Court of Justice in its jurisprudence, drawing on the administrative law of a number of member states.

25. The principle applies generally to legislative and administrative measures adopted by EU institutions. It also applies to national measures falling within the scope of EU law…
The principle only applies to measures interfering with protected interests…Such interests include the fundamental freedoms guaranteed by the EU Treaties.

26. It is also important to appreciate, at the outset, that the principle of proportionality in EU law is neither expressed nor applied in the same way as the principle of proportionality under the Convention for the Protection of Human Rights and Fundamental Freedoms ..

The division of responsibility between the Court of Justice and national courts


[This section is not included]

The nature of the test of proportionality [the three questions]

33. Proportionality as a general principle of EU law involves a consideration of two questions:
first, whether the measure in question is suitable or appropriate to achieve the objective pursued; and
secondly, whether the measure is necessary to achieve that objective, or whether it could be attained by a less onerous method.
There is some debate as to whether there is a
third question, sometimes referred to as proportionality stricto sensu: namely, whether the burden imposed by the measure is disproportionate to the benefits secured. In practice, the court usually omits this question from its formulation of the proportionality principle. Where the question has been argued, however, the court has often included it in its formulation and addressed it separately, ….

[The flexibility of proportionality]
34. Apart from the questions which need to be addressed, the other critical aspect of the principle of proportionality is the intensity with which it is applied. In that regard, the court has been influenced by a wide range of factors, and the intensity with which the principle has been applied has varied accordingly. It is possible to distinguish certain broad categories of case. It is however important to avoid an excessively schematic approach, since the jurisprudence indicates that the principle of proportionality is flexible in its application. The court’s case law applying the principle in one context cannot necessarily be treated as a reliable guide to how the principle will be applied in another context: it is necessary to examine how in practice the court has applied the principle in the particular context in question.

35. Subject to that caveat, however, it may be helpful to describe the court’s general approach in relation to three types of case:
[a] the review of EU measures,
[b] the review of national measures relying on derogations from general EU rights, and
[c] the review of national measures implementing EU law.

[EU Measures]
36. As a generalisation, proportionality as a ground of review of EU measures is concerned with the balancing of private interests adversely affected by such measures against the public interests which the measures are intended to promote. Proportionality functions in that context as a check on the exercise of public power of a kind traditionally found in public law. The court’s application of the principle in that context is influenced by the nature and limits of its legitimate function under the separation of powers established by the Treaties. In the nature of things, cases in which measures adopted by the EU legislator or administration in the public interest are held by the EU judicature to be disproportionate interferences with private interests are likely to be relatively infrequent.

[National measures]
37. Proportionality as a ground of review of national measures, on the other hand, has been applied most frequently to measures interfering with the fundamental freedoms guaranteed by the EU Treaties. Although private interests may be engaged, the court is there concerned first and foremost with the question whether a member state can justify an interference with a freedom guaranteed in the interests of promoting the integration of the internal market, and the related social values, which lie at the heart of the EU project. In circumstances of that kind, the principle of proportionality generally functions as a means of preventing disguised discrimination and unnecessary barriers to market integration. In that context, the court, seeing itself as the guardian of the Treaties and of the uniform application of EU law, generally applies the principle more strictly. Where, however, a national measure does not threaten the integration of the internal market, for example because the subject matter lies within an area of national rather than EU competence, a less strict approach is generally adopted. That also tends to be the case in contexts where an unregulated economic activity would be harmful to consumers, particularly where national regulatory measures are influenced by national traditions and culture…

38. Where member states adopt measures implementing EU legislation, they are generally contributing towards the integration of the internal market, rather than seeking to limit it in their national interests. In general, therefore, proportionality functions in that context as a conventional public law principle. On the other hand, where member states rely on reservations or derogations in EU legislation in order to introduce measures restricting fundamental freedoms, proportionality is generally applied more strictly, subject to the qualifications which we have mentioned.

39. Having provided that broad summary, it may be helpful to consider in greater detail the application of the principle of proportionality to EU and national measures in turn. [not included.]’

[Edited and formatted for ease of reading. Matter is square parentheses has been added as has emphasis].