Canon:Rule 0

"Have fun."

Dungeons and Dragons is a game, and as a game, it has rules. It is the job of the Dungeon Master to adjudicate these rules using the rulebooks. But when the rules allow something contextually nonsensical or disallows something that should be allowed, the Dungeon Master may change the rules.

Invoking Rule 0 is separate from using House Rules, since Rule 0 generally is invoked on one-time events.