Argument from the REDUNDANCE OF THE LAW
Ab inutilitate legi

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

The argument from the uselessness or superfluousness of the law is a matter of legal logic, see legal argument. Because it is based on the principle of legislative economy, it is also called the economy argument.

This argument requires that the code be designed as a system, so that none of its provisions paraphrase another. The code must be laconic (principle of non-redundancy).
This principle applies when several interpretations L1, L2, of the law L0 are possible. If it can be shown that one of these interpretations, say L1, makes L0 equivalent to another law Lx, belonging to the same code, then interpretation L1 must be rejected.
“Under interpretation I, the passage L0 becomes equivalent to the passage Lx, which then becomes redundant and useless. We must therefore favor an alternative interpretation of passage A”. This is a form of argument from the absurd (undesirable consequences). The new interpretation is sought, for example, in the intention of the legislator.

By extension, the argument from the superfluousness of the law applies to cases where the application of a law presupposes a state of fact. If teenagers under the age of 16 are not allowed to enter a nightclub, there is no need for a law prohibiting the sale or service of alcohol to them in such place; such a law would be superfluous.
But if it is forbidden to sell alcohol to people under the age of 16, s they are free to enter such establishments; otherwise the law forbidding them to consume alcohol would be superfluous.

Suppose a rule prohibits attendees at a meeting from voting on matters that directly affect them. The question then arises: Can attendees participate in discussions about these matters? Should the rule state that their presence at the meeting is permitted?

— Law redundancy argument: Yes, they can participate. No, there is no need for a specific rule. It is sufficient to say observe that you must be a member of the meeting in order to vote; if you are prohibited from voting, it is precisely because you are a member of the meeting. If you were not admitted in the meeting, then it would be superfluous to prohibit you from voting. No further explanation is needed.

— Argument “Things that are self-evident are better said”: So, let’s make the rule that “all those concerned may not vote but may participate in the discussion sessions of the issues that concern them”. The new rule is safer. In the first case, the cost is a subtle semantic inference; in the second, a slight redundancy.

The same principle of economy also applies to sacred texts. Consider the problem of applying the scheme of opposites to a prescription expressed as: “Do not do this under such and such circumstances”. In ordinary cases, the application of the rule of the opposites leads to the conclusion that: “Outside of these circumstances, you may do it”.

Sometimes the Qur’anic text explicitly mentions the opposite case (Khallâf,1942; Qur’an, 4-23), according to the scheme:

Do not do it under such and such conditions. Out of these conditions, you may do it.

Whereas in other cases, the opposite is not explicitly stated:

Do not do this under such and such conditions.

So the question in this second case is can one appeal to the scheme of the opposites to complete the text? If one adds “under other circumstances, do it!”, the literal precision given in the first case is rendered useless. Assuming that the Holy Text is perfect, it does not express anything useless or superfluous. In this case, no one has the right to add anything to it, or to infer anything about what should or should not be done.
If the supreme legislator is silent, the judge’s decision is based on tradition, or on some other recognized source of law.