Final answer:
Presidential directives with the weight of law are known as executive orders, which are legally binding and equivalent to laws, allowing the President to govern federal operations unilaterally.
Step-by-step explanation:
Presidential directives that have the same weight as law but are not voted on by Congress are called executive orders. Executive orders are issued by the President of the United States to direct the operations of the federal government. They are legally binding and are treated by the courts as equivalent to law. These directives allow the President to manage federal operations and to implement legislation. While Congress can overrule executive orders by changing the law, and such actions can also be challenged in court, they are a powerful tool used by presidents to enact policies without congressional approval. Some historical examples include Lincoln's Emancipation Proclamation and Truman's order to desegregate the armed forces. These orders stem from the constitutional mandate for the president to "take care that the laws be faithfully executed."