As the president and the executive department implement and enforce a law. they might need

As the president and the executive department implement and enforce a law. They might need "to interpret the details of a law".

The President is both the head of state and head of administration of the United States of America, and Commander-in-Chief of the military.

Under Article II of the Constitution, the President is in charge of the execution and implementation of the laws made by Congress. Fifteen official offices — each drove by a named individual from the President's Cabinet — complete the everyday organization of the government.