Proportionality essentially means the decision should meet a legitimate policy goal and should not go further than necessary to achieve that goal – i.e. it must be appropriate and necessary to achieve its aim.
In principle, the court is entitled to review the vast majority of decisions taken by public authorities; this is ‘in principle’ because there are still a handful of types of decisions with which the court is reluctant to concern itself – the award of honours is one example. Another may be where, because of the subject matter of the decision, the decision-maker is better qualified than the court to make a judgement. So, for example, the court is likely to ‘defer’ to, or recognise, a ‘demarcation of functions’ with the decision-maker in:
- ordering financial priorities, in deciding to spend public money in one way rather than another
- assessing the needs of national security and public order
- setting policy on maximum sentences for particular criminal offences.
In the demarcation of functions, that political judgement should be left to the decision-maker, who understands the policy and has experience of its operation to inform their decision. In this kind of area, the court may exercise restraint in reviewing the decision-maker, or recognise the demarcation of functions between the executive branch of government and the judiciary; the court is likely to allow a ‘margin of discretion’ or ‘discretionary area of judgement’ depending on the nature of the decision.