Custom, Customs

"Legal Lexicon":
CUSTOMS - This term is usually applied to those taxes which are payable upon goods and merchandise imported or exported.
Obs. Taxes paid by merchants and peasants for the use of roads, bridges, or the gates of boroughs; the common law.
CUSTOM. A usage which had acquired the force of law. It is in fact, a lex loci which regulates all local or real property within its limits. A repugnancy which destroys it must be such as to show it never did exist. In Pennsylvania no customs have the force of law but those which prevail throughout the state.
A custom derives its force from the tacit consent of the legislature and the people, and supposes an original, actual deed or agreement. Therefore, custom is the best interpreter of laws: optima est legum interpres consuetudo. It follows therefore, there can be no custom in relation to a matter regulated by law. Law cannot be established or abrogated except by the sovereign will, but this will may be express or implied and presumed and whether it manifests itself by word or by a series of facts is of little importance.
When a custom is public, peaceable, uniform, general, continued, reasonable and certain, and has lasted 'time whereof the memory of man runneth not to the contrary,' it acquires the force of law. And when any doubts arise as to the meaning of a statute the custom which has prevailed on the subject ought to have weight in its construction, for the manner in which a law has always been executed is one of its modes of interpretation.
Customs are general or particular customs. By general customs is meant the common law itself, by which proceedings and determinations in courts are guided.
Particular customs are those which affect the inhabitants of some particular districts only. --b--