Except for when the laws are commonly accepted on a basis of what is and is not "good sci fi". There are exceptions to rules, but not always. The rules are formed based on deductive reasoning of what is and is not considered "good sci fi". An example would be the "no [url=http://www.wikipedia.org/wiki/Godwin%27s_law]-godwinslaw!-[/url]" rule. [url=http://www.wikipedia.org/wiki/Godwin%27s_law]-godwinslaw!-[/url] are considering lazy writing by a large portion of the sci fi community. A large number of sci fi that includes [url=http://www.wikipedia.org/wiki/Godwin%27s_law]-godwinslaw!-[/url] is generally viewed as "bad", therefore, [url=http://www.wikipedia.org/wiki/Godwin%27s_law]-godwinslaw!-[/url] in sci fi are considered "bad sci fi". Hence the creation of the rule. A rule does not need to be enforced by an authority for it to be rule.