term:

Custom

custom n

1 : a practice common to many or to a particular place or institution
;esp
: a long-established practice that is generally recognized as having the force of law see also section 1983 compare usage
2
pl

a : duties, tolls, or imposts imposed by the law of a country on imports or exports
b usu sing in constr
: the agency, establishment, or procedure for collecting such customs

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.