IN THE BOOKS

The Warrior Code: IT IS STRICTLY FORBIDDEN TO HUNT ON OR TRESPASS OTHER CLANS' TERRITORY. TAKE ONE STEP INTO ANOTHER CLAN'S HUNTING GROUNDS AND YOU SHALL BE PUNISHED

IN WARRIOR CATS: UNTOLD TALES (It's a game, look it up)

Every single quest: TRESPASS AND STEAL THINGS FROM OTHER CLAN TERRITORIES FOR ME SO YOU GET REPUTATION AND DON'T GET EXILED

Yeah.