<P> The Preamble's reference to the "United States of America" has been interpreted over the years to explain the nature of the governmental entity that the Constitution created (i.e., the federal government). In contemporary international law, the world consists of sovereign states (or "sovereign nations" in modern equivalent). A state is said to be "sovereign," if any of its ruling inhabitants are the supreme authority over it; the concept is distinct from mere land - title or "ownership ." While each state was originally recognized as sovereign unto itself, the Supreme Court held that the "United States of America" consists of only one sovereign nation with respect to foreign affairs and international relations; the individual states may not conduct foreign relations . Although the Constitution expressly delegates to the federal government only some of the usual powers of sovereign governments (such as the powers to declare war and make treaties), all such powers inherently belong to the federal government as the country's representative in the international community . </P> <P> Domestically, the federal government's sovereignty means that it may perform acts such as entering into contracts or accepting bonds, which are typical of governmental entities but not expressly provided for in the Constitution or laws . Similarly, the federal government, as an attribute of sovereignty, has the power to enforce those powers that are granted to it (e.g., the power to "establish Post Offices and Post Roads" includes the power to punish those who interfere with the postal system so established). The Court has recognized the federal government's supreme power over those limited matters entrusted to it . Thus, no state may interfere with the federal government's operations as though its sovereignty is superior to the federal government's (discussed more below); for example, states may not interfere with the federal government's near absolute discretion to sell its own real property, even when that real property is located in one or another state . The federal government exercises its supreme power not as a unitary entity, but instead via the three coordinate branches of the government (legislative, executive, and judicial), each of which has its own prescribed powers and limitations under the Constitution . In addition, the doctrine of separation of powers functions as a limitation on each branch of the federal government's exercise of sovereign power . </P> <P> One aspect of the American system of government is that, while the rest of the world now views the United States as one country, domestically American constitutional law recognizes a federation of state governments separate from (and not subdivisions of) the federal government, each of which is sovereign over its own affairs . Sometimes, the Supreme Court has even analogized the States to being foreign countries to each other to explain the American system of State sovereignty . However, each state's sovereignty is limited by the U.S. Constitution, which is the supreme law of both the United States as a nation and each state; in the event of a conflict, a valid federal law controls . As a result, although the federal government is (as discussed above) recognized as sovereign and has supreme power over those matters within its control, the American constitutional system also recognizes the concept of "State sovereignty," where certain matters are susceptible to government regulation, but only at the State and not the federal level . For example, although the federal government prosecutes crimes against the United States (such as treason, or interference with the postal system), the general administration of criminal justice is reserved to the States . Notwithstanding sometimes broad statements by the Supreme Court regarding the "supreme" and "exclusive" powers the State and Federal governments exercise, the Supreme Court and State courts have also recognized that much of their power is held and exercised concurrently . </P> <P> The phrase "People of the United States" has sometimes been understood to mean "citizens ." This approach reasons that, if the political community speaking for itself in the Preamble ("We the People") includes only citizens, by negative implication it specifically excludes non-citizens in some fashion . It has also been construed to mean something like "all under the sovereign jurisdiction and authority of the United States ." The phrase has been construed as affirming that the national government created by the Constitution derives its sovereignty from the people, (whereas "United Colonies" had identified external monarchical sovereignty) as well as confirming that the government under the Constitution was intended to govern and protect "the people" directly, as one society, instead of governing only the states as political units . The Court has also understood this language to mean that the sovereignty of the government under the U.S. Constitution is superior to that of the States . Stated in negative terms, the Preamble has been interpreted as meaning that the Constitution was not the act of sovereign and independent states . </P>

What is the purpose of the constitution according to its preamble