A. Legal and Social Validity

It has been shown above that what applies to a system of norms need not necessarily apply to an individual norm. Systems of norms alone, then, will be considered first.

(i) Systems of Norms

A condition for the legal validity of a system of norms is that the norms belonging to the system be by and large socially efficacious, that is, socially valid.¹⁴ Only developed legal systems will be considered here.

¹⁴⁷ Sec Kelson. PTL § 34(g) (at pp. 212-13). and large socially efficacious, (hat is, are no longer by and large complied with or a sanction is no longer by and large imposed for non-compliance.

The question of the validity of a system of norms as a whole is posed with greatest clarity where two incompatible systems of norms compete. This situation may arise, say, in the case of a revolution, a civil war, or a secession. It is easy to say what is valid following the victory of one parly or the other. Then, the system of norms that has prevailed against the other system is valid, for its prevailing means that it is now the only system of norms that is by and large socially effica­cious. It is not so easy to say what is valid during the compe­tition between the systems of norms, that is, during the political struggle. There are three possibilities. The first is that neither of the two systems of norms is valid as a system of norms, because neither is by and large socially efficacious.

According to Hoersler, a characteristic of the concept of law is that a system of norms is a legal system, or is legally valid, only if it ‘prevails in the event of open conflict with other normative coercive systems in the society’.^14s This cri­terion may be called the ‘dominance criterion’. The domin­ance criterion, because it is contained in the criterion that a system of norms be by and large socially efficacious, adds nothing to that criterion. A system of norms that fails to prevail against other normative coercive systems is not by and large socially efficacious.

^,4X Hoerater. LR 184.

(ii) Individual Norms

An authoritatively issued norm of a legal system that is by and large socially efficacious does not forfeit its legal validity simply because it is frequently not complied with and a sanc­tion is only rarely imposed for non-compliance. Unlike legal systems, individual norms need not be by and large socially efficacious as a condition for legal validity. It is easy to see the reason for this difference. One may say of an individual norm that it is valid because it belongs to a legal system that is by and large socially efficacious. To say the same thing of a legal system, which could belong to no other legal system than itself, makes no sense.

There is, nevertheless, for individual norms, too, a relation between legal and social validity that can have consequences for legal validity in the event of a collision between the two. A condition for the legal validity of an individual norm is not, to be sure, that the norm be by and large socially efficacious, but, rather, that the norm exhibit a minimum social efficacy or prospect of social efficacy. Corresponding to this is the phe­nomenon of derogation through customary law (desuetudo), which consists in the forfeiture of the legal validity of a norm owing to a decline in the efficacy of the norm to a level below the minimum. Like the standard requiring that legal systems be by and large socially efficacious, this minimum for individual norms cannot in general—that is, apart from the case of com­plete inefficacy—be stipulated exactly. Thus, there can be cases where it is highly uncertain whether or not a norm has forfeited its legal validity owing to a derogation through customary law.