By-law

secondary city law, ordinance

A bylaw (sometimes also spelled by-law or byelaw) was originally the Viking town law in the Danelaw. Contrary to popular etymology the element by has nothing to do with the preposition by. It is the Old Norse word for larger settlement as in Whitby and Derby (compare with the modern Danish-Norwegian word "by" meaning town, or the modern Swedish word "by", meaning village).
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(n.)
A local or subordinate law; a private law or regulation made by a corporation for its own government.
  

(n.)
A law that is less important than a general law or constitutional provision, and subsidiary to it; a rule relating to a matter of detail; as, civic societies often adopt a constitution and by-laws for the government of their members. In this sense the word has probably been influenced by by, meaning secondary or aside.
  

A municipal, local or corporate rule or regulation. - (read more on By-law)