The president's powers – even seemingly unfettered ones, such as the power of the pardon – must be exercised within the parameters of other legal requirements derived from the Constitution or enacted by statute. To see this most clearly, consider a diverse group of people: the class of people who violated the Selective Service laws during the Vietnam War by burning their draft cards, fleeing to Canada, or through other, nonviolent acts of protest. President Jimmy Carter used the pardon power to grant clemency to everyone who had broken these laws in protesting the war – a merciful gesture by Carter, whatever your view on the merits of the conflict.