Which document outlines the foundational laws of the United States?

The Constitution is the foundational document that outlines the laws and principles governing the United States. It establishes the framework of the national government, delineating the powers of its three branches—executive, legislative, and judicial—while also outlining the rights of the states and the people. The Constitution serves as the supreme law of the land, meaning that any law or action by the government must conform to its provisions.

While the other documents mentioned have significant historical and legal importance, they serve different purposes. The Federalist Papers, for example, were written to support the ratification of the Constitution and clarify its meaning, but they do not serve as the governing document themselves. The Bill of Rights comprises the first ten amendments to the Constitution, ensuring specific protections for individual liberties but is part of the Constitution rather than a standalone document. The Declaration of Independence is a foundational text asserting the colonies' intent to separate from British rule and outlines principles of natural rights and government by consent; however, it does not establish the governing framework for the nation.

Thus, the Constitution is the primary document that articulates the fundamental laws and structure of the U.S. government, making it the correct answer.