The purpose of this paper was to find out whether the principle of equivalence of the judicial intervention in the penalty clause of Article 390 of the Emirati Civil Transactions Law can be harmonised with the functions which underpinned the institution. Comparative scholarship has understood that the judge can intervene, but not as if it were his duty, since, on both sides of the law, there is a threshold for the judge to cross before he can intervene and a measure to guide correction, which the comparative scholarship has combined in a single question. The comparative doctrinal approach is applied to statutory texts to distinguish threshold from measure, to create a fourfold typology of standards for intervention, and to compare the Emirati rule with the Egyptian, French and UNIDROIT standards. It finds that the Emirati text takes the lowest threshold in conjunction with the strictest measure (that is, the combination of these two elements renders the penalty clause redundant in the general rules on the assessment of damages) and that this combination eliminates the behavioural function without introducing an additional fairness benefit that is not already provided by the manifest excess test. Islamic jurisprudence allows for mitigation of excess and not identification with the actual harm. The study provides an analysis of such a typology, transferable to any other systems, and proposes to change the equivalence criterion by establishing a level of perceptible surplus and a corrective one of reduction to a reasonable quantity.