Secundum Usum Mercatorum Law and Legal Definition

The Latin maxim secundum usum mercatorum means according to the custom of merchants; that is, according to the law merchant.

The following is an example of a case law referring to secundum usum mercatorum:

Deeds or sealed instruments cannot be said to be made secundum usum mercatorum, since they find their recognition and validity in the more ancient rules of the common law. [Conine v. Junction & B. R. Co., 8 Del. 288, 300-301 (Del. 1866)].