Final answer:
When the president pardons someone for a federal crime, they are using their expressed constitutional power. This power is unequivocal and cannot be overturned by other branches of government.
Step-by-step explanation:
When the president grants a pardon to someone convicted of a federal crime, this is an example of using one of their expressed powers, as spelled out in the Constitution. The power to pardon is a unique executive action that cannot be overturned by other branches of government, and it has been used in various ways through history.
For instance, President Gerald Ford's pardon of his predecessor, Richard Nixon, and President Jimmy Carter's amnesty to Vietnam War draft dodgers are both examples of this executive authority. Although generally a rare occurrence, the use of this power can sometimes lead to controversy; however, its constitutional basis remains unequivocal as it is part of the constitutionally enumerated powers of the president.