How did the magna Carta gradually change legal ideas in England?

Before the Magna Carta, the King's Word was law. He needed no approval from anyone else to make laws. After the Magna Carta, the King officially recognized that his laws had to be acknowledged by the aristocracy (Barons). This began a shift from a single absolute legal authority (the monarch) to a diffusion of legal power down to the people ruled by the monarch. Presently legal authority in England rests with the hereditary aristocracy (House of Lords) and elected representatives (House of Commons) with very little real legal authority left to the monarch.