We must be ready to say that there is law wherever there is punishment on the part of a human society, whether acting in the mass, or through its representatives.

Punishment means the infliction of pain on one who is judged to have broken a social rule.

Conversely, then, a law is any social rule to the infringement of which punishment is by usage attached.

So long as it is recognized that a man breaks a social rule at the risk of pain, and that it is the business of everybody, or of somebody armed with the common authority, to make that risk a reality for the offender, there is law within the meaning of the term as it exists for anthropology.
Punishment, however, is by its very nature an exceptional measure.
It is only because the majority are content to follow a social rule, that law and punishment are possible at all.

If, again, every one habitually obeys the social rules, law ceases to exist, because it is unnecessary.