From the RuleBook:
"Slashing, piercing, or bludgeoning weapons more than 36 inches up to a maximum of 48 inches. The pommel and handle of the weapon can be no longer than 1/3 of the weapon’s total length. At least 2/3 of its length must be strike-legal."
Certain classes use Long Swords as a primary weapon. Certain classes cannot use Long Swords at all. If a Raider is using a Long Sword, he is in violation of the rules. He must retrieve a short sword, forgo the long sword, or sit out the rest of that battle.