A by-law (sometimes also spelled bylaw, by law or byelaw) is a rule or law established by an organization or community to regulate itself, as allowed or provided for by some higher authority. The higher authority, generally a legislature or some other governmental body, establishes the degree of control that the by-laws may exercise. By-laws may be established by entities such as a business corporation, a neighborhood association, or depending on the jurisdiction, a municipality.
In the United Kingdom, Canada, and some Commonwealth countries, the local laws established by municipalities are referred to as by-laws because their scope is regulated by the central governments of those nations. Accordingly, a bylaw enforcement officer is the Canadian equivalent of the American Code Enforcement Officer or Municipal Regulations Enforcement Officer. In the United States, the central government (and usually the state governments) has no direct ability to regulate the scope of the laws passed by the municipalities. As such terms such as code, ordinance, or regulation, if not simply law are more common.
The Oxford English Dictionary indicates that the origin of the current modern use of the word is not clear. One possibility is the earliest use of the term, which originates from the Viking town law in the Danelaw, wherein by is the Old Norse word for a 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). However, it is also possible that this usage was forgotten and the word was "reinvented" in modern times through the use of the adverbial prefix by- giving the meaning of subsidiary law or side-law (as in byway). In either case, it is incorrect to claim that the origin of the word is simply the prepositional phrase "by law."
Municipal By-laws 
Municipal by-laws are public regulatory laws which apply in a certain area. The main difference between a by-law and a law passed by a national/federal or regional/state body is that a bylaw is made by a non-sovereign body, which derives its authority from another governing body, and can only be made on a limited range of matters. A local council or municipal government gets its power to pass laws through a law of the national or regional government which specifies what things the town or city may regulate through bylaws. It is therefore a form of delegated legislation.
Within its jurisdiction and specific to those areas mandated by the higher body, a municipal by-law is no different than any other law of the land, and can be enforced with penalties, challenged in court and must comply with other laws of the land, such as the country's constitution. Municipal bylaws are often enforcable through the public justice system, and offenders can be charged with a criminal offence for breach of a bylaw. Common bylaws include vehicle parking and stopping regulations, animal control, building and construction, licensing, noise, zoning and business regulation, and management of public recreation areas.
By-laws in Japan 
By section 94 of the Constitution of Japan, regional governments have limited autonomy and legislative powers to create by-laws. In practice, such powers are exercised in accordance with the Regional Autonomy Law.
By-laws therefore constitute part of the legal system subordinate to the Japanese constitution. In terms of its mandatory powers and effective, it is considered the lowest of all legislation possible.
Such powers are used to govern the following;
- Location of the seat of government of the prefecture
- Frequency of routine meetings
- Number of prefectural vice-governors and vice village leaders
- Number of staff attached to administrative bodies governed
- Placement of regional autonomous areas
- Regulation of certain municipal monies
- Placement, maintenance and removal of public facilities
- Appointment of subordinate offices by the prefectural governor.
(from the Japanese Wikipedia)
United Kingdom 
Corporate bylaws 
Corporate and organisational bylaws regulate only the organisation to which they apply and are generally concerned with the operation of the organisation, setting out the form, manner or procedure in which a company or organisation should be run. Corporate bylaws are drafted by a corporation's founders or directors under the authority of its Charter or Articles of Incorporation.
Bylaws widely vary from organization to organization, but generally cover topics such as how directors are elected, how meetings of directors (and in the case of a business, shareholders) are conducted, and what officers the organization will have and a description of their duties. A common mnemonic device for remembering the typical articles in bylaws is NOMOMECPA, pronounced "No mommy, see pa!" It stands for Name, Object, Members, Officers, Meetings, Executive board, Committees, Parliamentary authority, Amendment.
Bylaws generally cannot be amended by an organization's Board of Directors; a super-majority vote of the membership, such as two-thirds present and voting or a majority of all the members, is usually required to amend bylaws.
In parliamentary procedure, particularly Robert's Rules of Order, the bylaws are generally the supreme governing document of an organization, superseded only by the charter of an incorporated society. The bylaws contain the most fundamental principles and rules regarding the nature of the organization. It was once common practice for organizations to have two separate governing documents, a constitution and bylaws, but this has fallen out of favor because of the ease of use, increased clarity, and reduced chance of conflict inherent in a single, unified document. This single document, while properly referred to as the bylaws, is often referred to as a constitution or a constitution and bylaws. Unless otherwise provided by law, the organization does not formally exist until bylaws have been adopted.
Union by laws 
In some countries, trade unions generally have constitutions, which govern activities of the international office of the union as well as how it interfaces with its locals. The locals themselves can set up their own bylaws to set out internal rules for how to conduct activities.
See also 
- Oxford English Dictionary online entry for "by-law" (subscription required)
- Answers.com entry for topic, "Bylaw Etymology"
- Robert, Henry M. (2000). Robert's Rules of Order Newly Revised, 10th ed., p. 553–562
- GMB Union rulebook – see rule 11.8 as an example