Final answer:
Congress has the constitutional authority to regulate trade with foreign nations according to the Commerce Clause in Article I, Section 8 of the U.S. Constitution.
Step-by-step explanation:
According to the Constitution, the authority to regulate trade with foreign nations is vested in Congress. This power is specifically granted to Congress in Article I, Section 8 of the Constitution. Congress asserts this authority through the power to regulate interstate commerce, as well as commerce with foreign nations and Indian tribes. This is often referred to as the Commerce Clause, which has been interpreted broadly by the Supreme Court, allowing Congress to legislate on a wide range of issues related to commerce.