Inasmuch as the jurisdiction of the federal courts in the classes of cases which may be within their jurisdiction is not exclusive, as already explained, unless expressly so declared, suits may be properly instituted in a state court (see above, § 143) which belong to some of the classes of cases of which a federal court may have jurisdiction. Under the rule that the court which first takes jurisdiction of the case should be allowed to proceed without interference from any other court, save a court of appeal, it would result that a case first brought in a state court, for instance, by a citizen of that state against a citizen of another state, or an alien, would be finally tried and determined in the state court, notwithstanding it was a case of which the federal courts might have jurisdiction, unless some provision were made for the removal of such a case from the state court to a federal court for trial. And the same considerations apply to a controversy arising under the constitution, laws, or treaties of the United States; for, as has already been said, the state courts are not excluded from the determination of such controversies.

Therefore, it is provided by the statutes of the United States, that the party against whom a suit is brought in a state court, which is of such character by reason of the subject-matter or the nature of the parties that it might have been brought in a federal court, may have it removed to the federal court for trial (Games v. Fuentes). This removal is secured by showing to the state court the facts which make the case a proper one for removal, and asking that it be transferred to the proper federal court. But even if the state court refuses to grant the transfer in a proper case, such transfer may be secured by application to the federal court to which the party applying has a right to have it removed. Such removal must, in general, be applied for before further proceedings are taken in the state court, and if the case is allowed to proceed before a removal is asked, it is too late to secure trial thereof in the federal court. But where the party asking to have the case removed can show that there is some prejudice or local influence making it improper that it be tried in the state court, he may secure a removal at a later stage in the proceedings, and thus have a trial in a tribunal free from such prejudice or local influence. It is, of course, impossible to state in detail the conditions and methods for removal of cases from the state to the federal courts, but the general principles in accordance with which such removals are allowed have been sufficiently indicated.