My very first contribution!

Ginevra's Principle states that, in any fandom of a work of fiction whose canon material is of predetermined length and comes from a restricted, consistent creator base (i.e. a book series with a single author, amirite?), there will be factions of fans whose..."ideas" for the canon material run contrary to the creators' plans and are, therefore, doomed to be proven wrong as the canon material reaches conclusion. Furthermore, the Principle observes that, the more specifically the creator(s) answer(s) the questions in debate by various fandom factions, the more members the contrary groups will lose to the vacuum of Real Life and Reasonable Behavior. However, at the same time, the smaller those groups become as their arguments are increasingly rendered null and void, the more batshit their theories will become, and the more intractably stubborn those fans will get in their "beliefs."

Ginevra's Law states that the activity of "debate" or "exchange" or "reasonable discussion" is logistically impossible and epistomologically inapplicable when dealing with these people. Any fan, no matter how well-intentioned or soundly argued, who attempts debate with the factions that bring Ginevra's Principle into action will be fined one week of Internet access for each attempt. Any fan from the Contrary Factions who attempts to trap an opponent into a "debate" over the issue in question will never be allowed to consume fictional materials again.

This law will also be known as The Law of JKR's Thesaurus