Argument ab inutilitate (legis); Lat. utilitas “utility, interest”, lex “law”; argument of uselessness (of the law).

The argument of the superfluity of the law is a matter of legal logic, S. Juridical Argument. As it is based on the principle of legislative economy, it is also referred to as the economy argument, or from uselessness argument.
This argument presupposes that the code is drawn as a system, so that none of its dispositions paraphrases another. The code is supposed to be laconic. So, an interpretation of a law that would make another law redundant, so superfluous, must be rejected: “Under interpretation I, passage A becomes equivalent to passage B, which then becomes redundant and useless. We must therefore favor an alternative interpretation of passage A”. This is a form of argumentation from the absurd (undesirable consequences). The new interpretation will be sought, for example, in the intention of the legislator.

By extension, the argument of the superfluity of the law applies to cases where the application of a law presupposes a state of fact. If entrance to a nightclub is denied to teenagers under 16, there is no need for a law prohibiting selling or serving alcohol to them in these places. Legislation on this would be superfluous.
But if it is forbidden to sell alcohol to people under 16, they might can freely attend these institutions; otherwise the law prohibiting the consumption of alcohol would be superfluous.

Let us assume that a regulation prohibits participants from voting on matters of direct concern to them. The question then is whether the participants can take part in discussions about these issues? Should it be specified in the regulation that their presence in the assembly is authorized?

— Argument by the superfluity of the regulation: Yes, they can participate. No, there is no need for a specific provision. Suffice it to observe that to vote one must be a member of the assembly; if you are forbidden to vote, it is precisely because you are part of the assembly. If you were not in the assembly, then it would be superfluous to forbid you to vote. No further clarification is needed.

— Argument “things which go without saying are better said”: so, let’s introduce the provision, “all those concerned do not take part in the vote but participate in the discussion sessions on the questions concerning them”. The new regulation is safer. In the first case, the price to pay is a subtle semantic inference; in the second, a slight redundancy.

Economy principle applied to sacred texts

The principle of economy applies to sacred texts. Consider the problem of the application of the scheme of the opposite to a prescription expressed as: “do not do this under such and such circumstances”. In ordinary cases, the application of the rule of the opposite leads to the conclusion that: “outside of these circumstances, you can do it”.

Sometimes the Koranic text explicitly mentions the opposite case (Khallâf,1942; Koran, 4-23), according to the scheme:

Do not do this under such and such conditions. Out of these conditions, do so.

Whereas in other cases, the contrary is not explicit:

Do not do this under such and such conditions.

The question in this second case is thus whether one can appeal to the scheme of the opposite to complete the text? If one adds “under other circumstances, do it!”, the literal precision given in the first case is rendered useless. If it is assumed that the Sacred Text is perfect, it expresses nothing useless or superfluous. In this case, nobody has the right to add to it, and to conclude anything about what to do or not to do.

The supreme legislator remaining silent, the judge’s decision will be founded on tradition, or on some other recognized source of legislation.