delivered the opinion of the court. After stating the case as above reported, he continued :

These cases come here under the act of March 3, 1885, ch. 353, 23 Stat. 437, which so.amends § 764 of the Revised Statutes as to give this court jurisdiction, upon appeal, to review the final decision of the Circuit Courts of the United States in certain specified- cases, including that of a writ of habeas corpus sued out in behalf of a person alleged to be restrained of his liberty in violation of the Constitution.

The first question to be considered is whether the Circuit Courts have jurisdiction on habeas corpus to discharge from custody one who is restrained of his liberty in violation of the National Constitution, but who, at the time, is held under State process for trial on an indictment charging him with an offence against the jaws of the..State.

The statutory provisions which control the determination of . this question are found in the following sections of the Revised Statutes:

“ Sec. 751. The Supreme Court and the Circuit and District Courts shall have power to issue writs of habeas corpus.

“ Sec. 752. The several justices and' judges of the said courts,within their respective jurisdictions, shall have power to grant writs of habeas corpus for the purpose of an inquiry into the cause of restraint of liberty.

*246 “ Sec. 753. The writ of habeas corpus shall in no case extend to a prisoner in jail, unless where he is in custody undér or by color of the authority of the United States, or is committed for trial before some court thereof; or is in custody for an act done or omitted in pursuance of a law or treaty of the United States, or of an order, process, or decree of a court or judge thereof; or,is in custody in violation of the Constitution, or of a law or.treaty of the United States; or being a subject or citizen of a foreign state, and domiciled therein, is in custody for an act done or omitted under any alleged right, title, authority, privilege, protection, or exemption claimed under the commission, or order, or sanction of any foreign state, or under color' thereof, the validity and effect whereof depend upon the law of nations; or unless it is necessary to bring the prisoner into court to testify.

■ “ Sec. 754. Application for the writ of habeas corpus shall be made to the court, or justice, or judge authorized to issue the same, by complaint in writing, signed by the person for whose relief it is intended, setting forth the facts concerning the detention of the party restrained, in whose custody he is detained, and by virtue of what claim or authority, if known. The facts set forth in the complaint shall be verified by the path of the person making the application.

“Sec. 755. The court, or justice, or judge to whom the application is made, shall forthwith award a writ of habeas corpus, unless it appears from the petition itself that the party is not entitled thereto. .The writ shall be directed to the person in whose custody the party is detained.”

“ Seo. 761. The court, or justice, or judge shall proceed in a summary way to determine the facts of the case, by hearing the testimony and arguments, and thereupon to dispose of the party as law and justice require.”

It is further provided, that, pending the proceedings on habeas corpus in cases mentioned in §§ 763 and 764: — which include an application for the writ by a'person alleged to be restrained of his liberty in violation of the Constitution of the United States — and, “ until final judgment therein, and after final judgment of discharge, any proceeding against the person *247 so imprisoned, or confined, or restrained of his liberty, in any State court, or by or under the authority of any State, for any matter so heard or determined, or in process of being heard and determined, under such writ of habeas corpus, shall be deemed null and void.”' § 766.

The grant to the Circuit Courts in § 751 of jurisdiction to issue writs of habeas corpus, is in language as broad as could well be employed. While it is attended by the general condition, necessarily implied, that the authority conferred must be exercised agreeably to the principles and usages of law, the only express limitation imposed is, that the privilege of the writ shall not be enjoyed by — or, rather, that the courts and the judicial officers named, shall not have power to award the writ to — -any prisoner in jail, except in specified cases, one of them being where he is alleged- to be held in custody in violation of the Constitution. The latter class of cases was first distinctly provided for by the. act of February 5, 1867,- ch. 28, 14 Stat. 385, which declares that the several courts.of the United States, and the several justices and judges thereof within their respective jurisdictions, in addition to the authority then conferred by law, “ shall have power to grant writs of habeas corpus in all cases where any person may be restrained of his or her liberty in violation of the Constitution, or of any treaty or law of the United States.” Whether, therefore, the appellant is a prisoner in jail, within the meaning of § 753, or is restrained of his liberty by an officer of the law executing the process of a court of Yirginia, in either case, it being alleged under oath that he is held -in custody in violation of the Constitution, the Circuit Court, has, by the express words of the statute, jurisdiction on habeas corpus to inquire into the cause fpr which he is restrained of his liberty, and to dispose of him “as.law and justice require.”

It may be suggested that the State court is competent to decide whether the petitioner is or is not illegally restrained of his liberty; that the appropriate time for the determination of that question is at the trial of the indictment; and that his detention for the purpose simply of securing his attendance at the trial ought not to be deemed an improper exercise by that *248 court of its power to bear and decide the case. The first of these propositions is undoubtedly sound; for in Robb v. Connolly, 111 U. S. 624, 637, it was held, upon full consideration, that “ a State court of original jurisdiction, having the parties before it, may, consistently with existing Federal, legislation, determine cases at law or in' equity, arising under the Constitution and laws of the United States, or involving rights dependent upon such Constitution or laws; ” and that “ upon the State courts, equally with the courts of the Union, rests the. obligation to guard, enforce, and protect every right granted or secured by the Constitution of the United States, and the. laws made in pursuance thereof, whenever those rights are-involved in any suit or proceeding before them.” But with respect to the other propositions, it is clear that, if the local' statute under which Royall was indicted be repugnant to the Constitution, the prosecution against him has nothing upon which to rest, and the entire proceeding against him is a nullity.- As was said in Ex parte Siebold, 100 U. S. 371, 376, “ An unconstitutional law is void, and is as no law. An offence created by it is not a crime. A conviction under it is not merely erroneous, but is illegal and void, and cannot be a legal Cause of imprisonment.” So in Ex parte Yarbrough, 110 U. S. 651, 654, it was said that if the statute prescribing the' offence for which Yarbrough and his associates were con- , victed was void, the court which tried them was without jurisdiction, and they were entitled to be discharged. It would seem — whether reference be had to the act of 1867 or to. existing statutory provisions — that it was the purpose of Com gress to invest the courts of the Union, and the justices and judges thereof, with power upon writ of habeas corpus, to ' restore to liberty any person, within their respective' jurisdictions, who is held in custody, by whatever authority, in violation of the Constitution or any law or treaty of the United States. The statute evidently contemplated that cases might arise when the power thus conferred should be exercised, during the progress of proceedings instituted against the petitioner in a State court, or by or under authority of a State, on account of the very matter presented for determination by the *249 writ of habeas corpus; for care is taken to provide that any such proceedings, pending the hearing of the case upon the writ and until final judgment and after the prisoner is discharged, shall be null and void. If such were not the clear implication of the statute, still, as it does not except from its operation cases in which the applicant for the writ is held in custody by the authority of a State, acting through its judiciary or by its officers, the court could not, against the positive language of Congress, declare any such exception, unless required to do so by the terms of the Constitution itself. But as the judicial power of the nation extends to all cases arising under the Constitution, the laws and treaties of the United States: as the privilege of the writ of habeas corpus cannot be suspended unless when in cases of rebellion or invasion the public safety may require it; and as Congress has power to pass all laws necessary and proper to carry into execution the powers vested by the Constitution in the Government of the United States or in any department or officer thereof; no doubt can exist as to the power of Congress thus to enlarge the jurisdiction of the courts of the Union and of their justices and judges. That the petitioner is held under1 the authority of a State cannot affect the question of the power or jurisdiction of the Circuit Court to inquire into the cause of his commitment, and to discharge him if he be restrained of his liberty in violation of the Constitution. The grand jurors who found the indictment, the court into which it was returned and by whose order he was arrested, and the officer who holds him in custody, are all, equally with individual citizens, under .a duty, from the discharge of which the State could not release them, to respect and obey the supreme law of the land, “ anything in the Constitution and laws of any State to the contrary notwithstanding.” 'And that equal power does not belong to‘ the courts and judges of the several States; that they cannot, under any authority conferred by the States, discharge from custody persons held .by authority of the courts of the United States, or of commissioners of such courts, or by officers of the General Government acting under its laws, results from’ the supremacy of the Constitution and laws of the United States. Ableman *250 v. Booth, 21 How. 506; Tarble's Case, 13 Wall. 397; Robb v. Connolly, 111 U. S. 624.

We are, therefore, of opinion that the Circuit Court has jurisdiction upon writ' of habeas corpus to inquire into the cause of appellant’s commitment, and to discharge him, if he be held in custody in violation of the Constitution.

It remains, however, to be considered, whether the refusal of that court to issue the writ and to take the accused from the custody of the State officer can be sustained upon any .other ground than the one upon which it proceeded. If it can be, the judgment will not be reversed because an insufficient reason may have been assigned for the dismissal of the petitions.

Undoubtedly the writ should be forthwith awarded, “ unless it appears from the petition itself that the party is not entitled thereto ; ” and the case summarily heard and determined “ as law and justice re'quire.” Such are the express requirements of the statute. If, however, it is apparent upon the petition, that the writ if issued dught not, on principles of law and justice, tp result in the immediate discharge of the accused from custody, the court is not bound to awai-d it as soon as the application is made. Ex parte Watkins, 3 Pet. 193, 201; Ex parte Milligan, 4 Wall. 2, 111. What law and justice may require, in a particular case, is often an embarrassing question to the court or to the judicial officer before whom the petitioner is brought. It is alleged in the petitions — neither one of which, however, is accompanied by a copy of the indictment in the State court, nor by any statement giving a reason why such a copy was not obtained — that the appellant is held in custody under process of a State court, in which he stands indicted for an alleged offence against the laws of Yirginia. It is stated in one case that he gave bail, but was subsequently surrendered by his sureties. But it is not alleged and it does not appear, in either case, that he is unable to give security for his appearance- in the State court, or that reasonable bail is denied him, or that his trial will be unnecessarily delayed. The question as to the constitutionality of the law under which he is indicted must necessarily arise at his trial under the indictment, and it is one upon which, as we have seen, it is competent for the State court to pass. *251 Under such circumstances, does the statute imperatively require the Circuit Court, by writ of habeas corpus, to wrest the petitioner from the custody of the State officers in advance of his trial in the State court? We are of opinion that while the Circuit Court has the power to do so, and may discharge the accused in advance of his trial if he is restrained of his liberty in violation of the national Constitution, it is not bound in every case to exercise such a power immediately upon application being made for the writ. We cannot suppose that Congress intended to compel those courts, by such means, to draw to themselves, in the first instance, the control of all criminal prosecutions commenced in State courts exercising authority within the same territorial limits, where the accused claims that he is held in custody in violation of the Constitution of the United States. The injunction to hear the case summarily, and thereupon “to dispose of,the party as law and justice require” does not deprive the court of discretion as to the time and mode in which it will exert the powers conferred upon it. That discretion should be exercised in the light of the relations existing, under our system of government, between the judicial tribunals of the Union and of the States, and in recognition of the fact that the public good requires that those relations be not disturbed by unnecessary conflict between courts equally bound to guard and protect rights secured by the Constitution. When the petitioner is in custody by State authority for an act done or omitted to be done in pursuance of a law of the United States, or of an order, process, or decree of a court or judge thereof; or where, being a subject or citizen of a foreign State, and domiciled therein, he is in custody, under like authority, for an act done or omitted under any alleged right, title, authority, privilege, protection, or;exemption claimed under the commission, or order, or sanction of any foreign State, or under color thereof, the validity and effect whereof depend upon the law of nations; in such and like cases of urgency, involving the authority and operations of the General Government, or the obligations of this country to, or its relations .with, foreign nations, the courts of the United States have frequently interposed by writs of habeas corpus and discharged prisoners who *252 were held in custody under State authority. So, also, when they are in the custody of a State officer, it may be necessary, by use of the writ,'to bring them into a court of the United States to testify as witnesses. The present cases involve no such considerations. Nor do their circumstances, as detailed in the petitions, suggest any reason why the State court of original jurisdiction may not, without interference upon the part of the courts of the United States, pass upon the question which is raised as to the constitutionality of the statutes under which the appellant is indicted. The Circuit Court was not at liberty, under the circumstances disclosed, to presume that the decision of the State court would be otherwise than is required by the fundamental law of the land, or that it would disregard the settled principles of constitutional law announced by this court, upon which is clearly conferred the power to decide ultimately and finally all cases arising under the Constitution and laws of the United States. In Taylor v. Carryl, 20 How. 583, 595, it was said to be a recognized portion of the duty of this court — and, we will add, of all other courts, National and State — “ to give preference to such principles and methods of procedure as shall serve to conciliate the distinct and indepen- dent tribunals of the States and of the Union, so that they may cooperate as harmonious members of a judicial system coextensive with the United States, and submitting to the paramount authority of the same Constitution, laws, and Federal obligations.” And in Covell v. Heymam, 111 U. S. 176, 182, it was declared “ that the forbearance which courts of co-ordinate jurisdiction, administered under a single system, exercise towards each other, whereby conflicts are avoided, by avoiding interference with the process of each other, is a principle of comity, with perhaps no higher sanction than the utility which comes from concord; but between State courts and those of the United States it is something more. It is a principle of right and of law, and, therefore, of necessity.”

That these salutary principles may have full operation, and in harmony with what we suppose was the intention of Congress in the enactments in question, this court holds that where a person is in custody, under process from a State court of *253 original jurisdiction, for an alleged offence against the laws of such State, and it is claimed that he is restrained of his liberty in violation of the Constitution of the United States, the Circuit Court has a discretion, whether it will discharge him, upon habeas corpus, in advance of his trial in the court in which he is indicted.; that discretion, however, to be subordinated to any special circumstances requiring immediate action. "When the State court shall have finally acted upon the case, the Circuit Court has still a discretion whether, under all the circum- stances then existing, the accused, if convicted, shall be put to his writ of error from the highest court of the State, or .whether it will proceed, by writ of habeas corpus, summarily to determine whether the petitioner is restrained of his liberty in violation of the Constitution of the United States. The latter was substantially the course adopted in Ex parte Bridges, 2 Woods, 428. The prisoner was indicted and convicted in one of the courts of Georgia for perjury committed in ah examination before a United States commissioner under what is known as the Enforcement Act of Congress. He was discharged upon habeas corpus, sued out before Mr. Justice Bradley, upon the ground that the State court had no jurisdiction of the case, the offence • charged being one which, under the laws of the United States, was exclusively cognizable in the Federal courts. Adverting to the argument that where a defendant has been regularly indicted, tried, and convicted in a State court, his only remedy was to carry the judgment to the State court of last, resort, and thence’ by writ of error to this court, he said: “ This might be so if the proceeding in the State court was merely erroneous; but where it is void for want of jurisdiction, habeas corpus will lie, and may be issued by any court or judge invested with .supervisory jurisdiction in such . case. Ex parte Lange, 18 Wall. 163.” It was further ob- ' served, in the same case, that while it might appear unseemly ■that a prisoner, after conviction in a State court, should be set at liberty by a single judge on habeas corpus, there was no escape from the act of 1867, which invested such judge with power to discharge when the. prisoner was restrained of his liberty in violation of a law of the United States.

*254 As it does not appear that the Circuit Court might not, in its discretion and consistently with law and justice, have denied the applications for the writ at the time they were made, we are of opinion that the judgment in each case must be affirmed, but without prejudice to the right of the petitioner to renew his applications to that court at some future time should the circumstances render it proper to do so.

Affirmed.