Source : Webster's Revised Unabridged Dictionary (1913)

By-law \By"-law`\ (b[imac]"-l[add]`), n. [Cf. Sw. bylag, D.
   bylov, Icel. b[=y]arl["o]g, fr. Sw. & Dan. by town, Icel.
   b[ae]r, byr (fr. b[^u]a to dwell) + the word for law; hence,
   a law for one town, a special law. Cf. {Birlaw} and see
   {Law}.]
   1. A local or subordinate law; a private law or regulation
      made by a corporation for its own government.

            There was likewise a law to restrain the by-laws, or
            ordinances of corporations.           --Bacon.

            The law or institution; to which are added two
            by-laws, as a comment upon the general law.
                                                  --Addison.

   2. 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.