Under the second head fall three types of cases: First, controversies between citizens of the same state claiming lands under grants of different states. Second, cases of admiralty and maritime jurisdiction, and third, cases in law or equity arising under the Constitution or laws of the United States, or treaties made under their authority.

568. THE WRIT OF HABEAS CORPUS. [Footnote: For the general arrangement of the material in Sections 568-570, I am indebted to Professor Beard's American Government and Politics, to which text acknowledgment is here made.]—In the exercise of their judicial functions the Federal courts have the power of issuing three great writs affecting the rights of citizens.

Of these the most famous is the writ of habeas corpus. This writ is designed to secure to any imprisoned person the right to have an immediate preliminary hearing for the purpose of discovering the reason for his detention. Where the writ is properly issued, the prisoner is brought into court for a summary examination. If it is found that he has been detained in violation of law, he is released; if not, he is remanded for trial.

Federal judges may not issue writs of habeas corpus indiscriminately. A writ can be issued only in the following cases: First, when a prisoner is in jail under Federal custody or authority; second, when an individual is in jail for some act done or omitted in pursuance of a law of the United States or the order, process, or decree of some Federal court or judge; third, when an individual has been detained because of violation of the Constitution or some law or treaty of the United States; and fourth, when a citizen of a foreign country claims to be imprisoned for some act committed with the sanction of his government.

569. THE WRIT OF MANDAMUS.—The writ of mandamus may be used against public officials, private persons, and corporations, for the purpose of forcing them to perform some duty required of them by law. Properly used, the writ of mandamus is called into action to compel executive officers to perform some administrative duty. The court will not intervene, however, where the duty is purely discretionary and its performance dependent either upon the pleasure of the official, or upon his interpretation of the law. Usually the applicant for a writ of mandamus must show that he has no other adequate legal remedy, and that he has a clear legal right to have the action in question performed by the officer.

570. THE WRIT OR BILL OF INJUNCTION.—This writ may be of several distinct types. It may take the form of a mandatory writ, ordering some person or corporation to maintain a status quo by performing certain acts. For example, striking railway employees may be ordered to continue to perform their regular and customary duties while remaining in the service of their employer.

The injunction may take the form of a temporary restraining order forbidding a party to alter the existing condition of things in question until the merits of the case have been decided. This is often used in labor disputes.

Sometimes the writ is in the form of a permanent injunction ordering a party not to perform some act, the results of which cannot be remedied by any proceeding in law. This, too, has often been used in labor disputes.

571. JUDICIAL INTERPRETATION OF THE STATUTES.—The crowning feature of the American judiciary is its power to pass upon the constitutionality of state and Federal laws. The Constitution does not give to the courts the power to declare state or Federal statutes invalid on the ground that they conflict with the Federal Constitution, but in the famous case of Marbury v. Madison in 1803, Chief Justice Marshall demonstrated that under the Constitution the Supreme Court must possess the power of declaring statutes null and void when they conflict with the fundamental law of the land. In deciding against the validity of a law, the court does not officially annul it, but merely refuses to enforce the statute in the particular case before the court. Thereupon, the executive officials who might be charged with the administration of that particular law, neglect to enforce it.

572. GENERAL POLICY OF THE FEDERAL COURTS.—The Federal courts have consistently refused to decide abstract questions not presented in the form of a concrete case between parties to an actual suit. The Supreme Court, for example, will take no notice of a statute until the question of its constitutionality arises in the form of a concrete case.