A principle that states state action should be commensurate to the seriousness of the issue at hand.
(Yeung cited in Morgan and Yeung 2007, 201-202)
The following notes on the proportionality principle are drawn from Yeung, cited in Morgan and Yeung 2007, 201-202:
“The concept of proportionality involves the evaluation of three factors: the suitability of the measure for the attainment of the desired objective, the necessity of the measure (in the sense that the state has no other option at its disposal which is less restrictive of the citizen’s freedom) and the proportionality of the measure to the restrictions which are thereby involved, including the burdens imposed on affected persons. In other words, proportionality entails some idea of balance, and of proper relationship between ends and means. The proportionality principle may, however, be inherently difficulty to apply because it is not an independent principle of review. Rather, it refers to the relationship between other specific and possibly competing substantive interests, requiring an articulation of the relevant benchmark for evaluating proportionality.
Given that the focus of the present inquiry is to identify the level of punitiveness that ought to inform the regulator’s response to a suspected contravention, the relevant benchmark is the nature and seriousness of the suspected wrongdoing which […] may be defined in terms of harm and culpability. Thus the seriousness of a contravention will be determined by a multiplicity of factors, including the degree of harm caused by the contravention, the deliberateness of the breach, the duration of the contravention, and the existence of prior contravening conduct by the firm concerned.”
Morgan, Bronwen and Karen Yeung. 2007. An Introduction to Law and Regulation: Text and Materials. Cambridge, UK; New York: Cambridge University Press.