Another basic concept embodied in the Constitution is federalism, which refers to the division and sharing of power between the national and state governments. By allocating power among state and federal governments, the Framers sought to establish a unified national government of limited powers while maintaining a distinct sphere of autonomy in which state governments could exercise a general police power. Although the Framers' sought to preserve liberty by diffusing power, Justices and scholars have noted that federalism has other advantages, including that it allows individual states to experiment with novel government programs as laboratories of democracy and increases the accountability of elected government officials to citizens.

Although the text of the Constitution does not clearly delineate many of the boundaries between the powers of the federal and state governments, the Supreme Court has frequently invoked certain constitutional provisions when determining that Congress has exceeded its constitutional powers and infringed upon state sovereignty. One well-known provision, regarded by the Court as both a shield and sword to thwart federal encroachment, is the Tenth Amendment, which provides that the powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people. In modern times, the Court has vacillated between the view that the Tenth Amendment operates to restrict Congress' power and the view that the amendment is a mere truism that cannot be used to strike down federal statutes. Other notable provisions addressing Congress' power relative to the states that the Court has debated include the Supremacy Clause in Article VI, which establishes federal law as superior to state law; the Commerce Clause in Article I, Section 8, Clause 3, which grants Congress the authority to legislate on matters concerning interstate commerce; and Section 5 of the Fourteenth Amendment, which grants Congress the power to enforce that Amendment's guarantees against the states through the enactment of appropriate legislation. More broadly, federalism principles also undergird many Supreme Court decisions interpreting individual rights and the extent to which the Court should federalize, for example, the rights afforded to state criminal defendants. But judges and scholars disagree on how basic principles of federalism should be realized, and a key point of controversy is whether the judiciary should enforce the interests of the states against the federal government or leave the resolution of such key questions about the relationship between federal and state power to the political process.

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The Constitution's Basic Principles: Federalism ...