An attorney general's duty is to render her opinion and honest advice; she cannot set herself up as a judge overruling the president's decision. The president need not 'convince' his subordinate that his decision reflects the best view of the law.

In our system of government, the Supreme Court ultimately decides on the constitutionality of laws passed by Congress or of presidential actions. When their actions are challenged, both Congress and the president are entitled to have their positions forcefully advocated in court.

Presidential powers are not exercised by a body or group. The Constitution vests 'all executive power' in one and only one person - the president.

William Barr Quotes