The United States has sovereign power to prescribe electoral qualifications for its own citizens; it has chosen to adopt State qualifications. The non-exercise of the power does not work denial of its existence. The principle involved is one of sovereignty, that non-user of a sovereign right cannot invalidate the right. 166. While the Fourteenth Amendment added nothing to the rights and privileges of citizens, for “the equality of the rights of citizens is a principle of republicanism,”[468] it guaranteed those rights; but “the power of the national government is limited to the enforcement of the guaranty.”[469] The Amendment does not invest Congress with power to legislate upon subjects which are within the domain of State legislation; but to provide modes of relief against State legislation, or State action “which impairs the privileges and immunities of citizens of the United States, or which injures them in life, liberty, or property without due process of law, or which denies to them the equal protection of the laws.”[470] Congress is empowered by the Amendment “to adopt appropriate legislation for correcting the effects of such prohibited State laws and State acts, and thus to render them effectually null, void, and innocuous.”[471] The essential matter here involved is sovereignty. The true doctrine is, that whilst the States are really sovereign as to all matters which have not been granted to the jurisdiction and control of the United States, the Constitution and constitutional laws of the latter are the supreme law of the land; and when they conflict with the laws of the States, they are of paramount authority and obligation. This is the fundamental principle on which the authority of the Constitution is based; and unless it be conceded in practice, as well as theory, the fabric of our institutions, as it was contemplated by its founders, cannot stand. The questions involved have respect not more to the autonomy and existence of the States, than to the continued existence of the United States as a government to which every American citizen may look for security and protection in every part of the land.[472] Thus, in application of this principle, the law of a State discriminating against persons of color by eliminating them to serve as jurors is unconstitutional.[473] So too is an act of Congress unconstitutional, that operates as, or creates, a municipal law for the regulation of private rights, and that places Congress in the stead, or office of the State legislatures, so that the federal Legislature, instead of enacting laws corrective of prohibited State laws, or counteracting such laws, assumes the office of the State legislatures in their general legislation. Such Congressional legislation “steps into the domain of local jurisprudence.”[474]