Mr. Justice BRENNAN delivered the opinion of the Court.

... This civil action was brought to redress the alleged deprivation of federal constitutional rights. The complaint alleges that by means of a 1901 statute of Tennessee apportioning the members of the General Assembly among the State's 95 counties, "these plaintiffs and others similarly situated are denied the equal protection of the laws accorded them by the Fourteenth Amendment to the Constitution of the United States by virtue of the debasement of their votes"...

Tennessee's standard for allocating legislative representation among her counties is the total number of qualified voters resident in the respective counties, subject only to minor qualifications. Decennial reapportionment in compliance with the constitutional scheme was effected by the General Assembly each decade from 1871 to 1901. In 1901 the General Assembly abandoned separate enumeration in favor of reliance upon the Federal Census and passed the Apportionment Act here in controversy. In the more than 60 years since that action, all proposals in both Houses of the General Assembly for the reapportionment have failed to pass.

Between 1901 and 1916, Tennessee has experienced substantial growth and redistribution of her population. In 1901 the population was 2,020,616, of whom 487,380 were eligible to vote. The 1960 Federal Census reports the State's population at 3,567,089, of whom 2,092,891 are eligible to vote. The relative standings of the counties in terms of qualified voters have changed significantly. It is primarily the continued application of the 1901 Apportionment Act to this shifted and enlarged voting population which gives rise to the present controversy.

The complaint alleges that the 1901 statute, even as of the time of its passage, "made no apportionment of Representatives and Senators in accordance with the constitutional formula, but instead arbitrarily and capriciously apportioned representatives in the Senate and House without reference to any logical or reasonable formula whatever." It is further alleged that "because of the population changes since 1900, and the failure of the Legislature to reapportion itself since 1901," the 1901 statute became "unconstitutional and obsolete." Appellants also argue that because of the composition of the legislature effected by the 1901 Apportionment Act, redress in the form of a state constitutional amendment to change the entire mechanism for reapportioning or any other change short of that, is difficult or impossible. The complaint concludes that "these plaintiffs and others similarly situated are denied the equal protection of the laws accorded them by the Fourteenth Amendment to the Constitution of the United States by virtue of the debasement of their votes." They seek a declaration that the 1901 statute is unconstitutional ...

With the plaintiffs' argument that the legislature of Tennessee is guilty of a clear violation of the state constitution and of the rights of the plaintiffs the Court entirely agrees. It also agrees that at the evil is a serious one which should be corrected without further delay. But even so the remedy in this situation clearly does not lie with the courts. It has long been recognized and is accepted doctrine that there are indeed some rights guaranteed by the Constitution for the violation of which the courts cannot give redress.

Since the complaint plainly sets forth a case arising under the Constitution. the subject matter is within the federal judicial power defined in Art. 111, Section 2, and so within the power of Congress to assign to the jurisdiction of the District Courts. Congress has exercised that power in [various U.S. codes.]

These appellants seek relief in order to protect or vindicate an interest of their own, and of those similarly situated. Their constitutional claim is, in substance. that the 1901 statute constitutes arbitrary and capricious state action, offensive to the Fourteenth Amendment in its irrational disregard of the standard of apportionment prescribed by the State's Constitution or of any standard, effecting a gross disproportion of representation to voting population.

"Under [Article IV] of the Constitution it rests with Congress to decide what government is the established one in a State. For as the United States guarantee to each State a republican government, Congress must necessarily decide what government is established in the State before it can determined whether it is republican or not. ... Congress was not called upon to decide the controversy. Yet the right to decide is placed there, and not in the courts.

We conclude that the complaint's allegations of a denial of equal protection present a justificiable constitutional cause of action upon which appellants are entitled to a trial and a decision. The right asserted is within the reach of judicial protection wider the Fourteenth Amendment.