The barons wanted King John to stop seizing their grain. The fish weirs had to go, too. Wikimedia Commons hide caption itoggle caption Wikimedia Commons The Salt 13th-Century Food Fights Helped Fuel The Magna Carta April 18, 2012 A greedy king who seized food was a key driver of the Magna Carta. That 13th-century document was a key inspiration for the American Revolution 500 years later. But at the time, the barons who negotiated the deal weren't concerned with the rights of starving peasants — these 1 percenters wanted to protect their own power and property.