Custom & Usage

Custom is the best interpreter of the law.

Optima est legis interpres consuetudo.

Source: Dig. 1.3.37; 2 Inst. 18; Broom, Max. 931; Jenk. Cent. 273

When the meaning of a law is disputed, the long-established practice of the People under that law is the surest guide to its true intent.

Custom is another law.

Consuetudo est altera lex.

Source: Coke, 4 Co. 21; Co. Litt. 113; Weisman, 27d; Weisman, 27e; Weisman, 27n

Custom operates with the force of enacted law — a party who violates an established custom faces the same consequences as one who violates a statute.

A custom must be certain, for an uncertain custom is held as nothing.

Consuetudo debet esse certa; nam incerta pro nulla habetur.

Source: Davies 33; Black's 255; Bouvier, Max. 121; Weisman, 27c

A custom too vague to be stated with precision cannot bind — the party asserting custom must prove its definite content and consistent application.

A custom, however great its authority, should never prejudice manifest truth.

Consuetudo, licet sit magnae auctoritatis, nunquam tamen praejudicat manifestae veritati.

Source: Coke, 4 Co. 18; Weisman, 27i

No custom, however ancient or universal, can override plain truth — when custom and fact collide, fact prevails.

A custom grounded on a certain and reasonable cause supersedes the common law.

Consuetudo certa et rationabili causa superinducta vincit legem communem.

Source: Litt. s. 169; Co. Litt. 113; Broom, Max. 919; Weisman, 27h

Where a local custom rests on solid reason and has been consistently observed, it displaces the general common law rule for that locality.

Where it is unclear what was agreed, we follow the usage of the place where the agreement was made.

Si non apparet quid actum est, erit consequens ut id sequamur quod in regione in qua actum est frequentatur.

Source: Dig. 50, 17, 34

Local custom fills the gaps where the parties have been silent on a term — the law presumes they intended what is customary.

In contracts, matters of custom and usage are tacitly implied.

In contractibus tacite insunt quae sunt moris et consuetudinis.

Source: Story, Bills, s. 143; 3 Kent, Comm. 260n; Broom, Max. 842; Weisman, 24n

The parties are presumed to contract with reference to known customs of their trade or locality — these become part of the agreement by implication.