 The barons were not militarily powerful enough to win a decisive victory, and instead appealed to Louis IX of France in 1263–1264 to arbitrate on their proposed reforms.The reformist barons argued their case based on Magna Carta, suggesting that it was inviolable under English law and that the King had broken its terms.Louis came down firmly in favour of Henry, but the French arbitration failed to achieve peace as the rebellious barons refused to accept the verdict.