Article One of the United States Constitution
Section 1 gives federal legislative power exclusively to Congress. Similar clauses are found in Articles II and III. The former gives executive power to the President. The latter grants judicial power to the federal judiciary. These three articles create a separation of powers among the three branches of the federal government. The separation of powers was intended to limit Congress to making law, the President to enforcing the law and the courts as interpreting the law in different cases.