Excerpts from Books and Wikipedia
"When Edward ignored the summons [after Philip ordered him to appear at his court], Philip confiscated Aquitaine as punishment. Edward immediately began to round up allies on the continent. . . . He also sent an imperious message to John Balliol, ordering him to send Scottish troops as part of his feudal responsibility to his overlord. Balliol sent back a meek reply, promising the soldiers; but at this, the aristocrats who had chosen him took the country out of his hands. Twelve of them formed a council to govern the country, and “it was decreed,” says the Chronicle of Lanercost, “that the king could do no act by himself.” . . . Now Edward was faced with the necessity of fighting in both France and Scotland; in France, as a disobedient vassal; in Scotland, as the overlord of a disobedient vassal. Leaving the French war in the hands of his generals, he personally led an army towards the Scottish city of Berwick. . . . The Scottish defenders were driven steadily back into the north. One by one the castles of Scotland fell . . . But none of the Twelve Peers emerged as the leader of Scottish rebellion." That role fell to William Wallace. [Bauer: Renaissance World, p. 394-400]