Conduct

Duels are permitted only in the sunken Court, only before a witness, and only to first yield. Wands lowered when an opponent falls. To break the Code is to answer to the Headmistress, and no one does that twice.

Three things are forbidden within these walls: magic that bends a mind against its will, magic that wakes the dead, and any door that opens onto the Veil. Each rule was written in someone's blood. The school does not explain whose.