I join the court’s opinion, which analyzes the record and persuasively shows that the state court did not act “arbitrarily” in setting Garcia’s bond at $607,000. The court answers the only question the sheriff put to us. Yet it should not pass unnoticed that the sheriff asked the wrong question.
Judge Kowalski of the Circuit Court of Cook County decided what bail to set. The appellate court affirmed. The Supreme Court of Illinois reviewed the case and affirmed in turn. The district court proceeded as if it had under consideration a direct appeal from the decision of the Supreme Court of Illinois. And now we have the direct appeal from the district court— making us the fifth court (and the thirteenth, fourteenth, and fifteenth judges) to ask whether $607,000 is the right amount of bail.
In exercising an “appellate” jurisdiction over the Supreme Court of Illinois, the district court asked whether Judge Kowalski had misunderstood — or, if he under*356stood, misapplied — the bail statute of Illinois. See Ill.Rev.Stat. ch. 38 11110-5(b)(4), which states: “When a person is charged with a drug related offense ... the full street value of the drugs seized shall be considered.” The district court expressly found that the circuit court, and presumably the Supreme Court of Illinois, had erred in the application of Illinois law. As the district court put it, the state judges acted “on the mistaken assumption the Illinois General Assembly has equated street value with reasonable bail. It has not. There is no unconstitutional infirmity in the Act — only in its erroneous application here.” Garcia v. Elrod, 643 F.Supp. 922, 925 (N.D.Ill.1986) (footnote omitted). As the sheriff has briefed the case, we are to decide who correctly understood Illinois law, the state courts or the federal district judge.
Yet a federal court may not disagree with the state courts’ construction of state law. Herb v. Pitcairn, 324 U.S. 117, 125-26, 65 S.Ct. 459, 463-64, 89 L.Ed. 789 (1945). State law means what state judges say it means, just as federal law means (for the purposes of judges of inferior federal courts) what the Supreme Court of the United States concludes it means. If eleven state judges, including a unanimous Supreme Court of Illinois, say that $607,000 is the right bail, they have defined the meaning of state law. The decision of the Supreme Court of Illinois on a question of state law cannot be “mistaken” for the purposes of a federal court. It may be mistaken in the sense that the state judges later will reverse themselves, or the legislature will declare that the judges have not grasped the purport of the law; but it is not mistaken in the sense that a federal court may set aside the judgment. So far as the federal courts are concerned, the circuit court adhered scrupulously to the law of Illinois. We must ask not whether Judge Kowalski obeyed state law, but whether his decision violated the eighth amendment to the Constitution.
A federal court may encounter a genuine error of state law when an appellate court within a state declares that the trial court made a mistake. Then it may be necessary to ask whether the error of state law violated the Constitution. Even so, an error is not itself a violation of the Constitution. It is not enough to issue the writ of habeas corpus, as the district court did. The statute governing writs of habeas corpus provides that a federal judge may release a state’s prisoner only if the custody is “in violation of the Constitution or laws or treaties of the United States”. 28 U.S.C. § 2241(c)(3). “A federal court may not issue the writ on the basis of a perceived error of state law.” Pulley v. Harris, 465 U.S. 37, 41, 104 S.Ct. 871, 875, 79 L.Ed.2d 29 (1984). See also Engle v. Isaac, 456 U.S. 107, 119-21 & n. 21, 102 S.Ct. 1558, 1567-68 & n. 21, 71 L.Ed.2d 783 (1982). Cf. Pennhurst State School & Hospital v. Halderman, 465 U.S. 89, 106, 104 S.Ct. 900, 911, 79 L.Ed.2d 67 (1984) (“it is difficult to think of a greater intrusion on state sovereignty than when a federal court instructs state officials on how to conform their conduct to state law.”).
The eighth amendment potentially makes errors of state law pertinent through the definition of “excessive” bail. That language comes from the Bill of Rights of 1689, 1 Wm. & Mary, 2d Sess., ch. II, § I(10). See 4 William Blackstone, Commentaries on the Law of England *294-96 (1769). It grew out of struggles between Parliament and the Crown, and a principal function of the provisions from which it was derived was to prevent the King’s judges from abrogating the distinction between bailable and nonbailable (capital) offenses. See United States v. Edwards, 430 A.2d 1321 (D.C.1981) (en banc), which contains a thorough and thoughtful discussion of the background of the bail clause of the eighth amendment. We took the language wholesale, and “when this clause was carried over into our Bill of Rights, nothing was said that indicated any different concept.” Carlson v. Landon, 342 U.S. 524, 545, 72 S.Ct. 525, 536-37, 96 L.Ed. 547 (1952) (footnote omitted). When the legislature wants bail to be available for those arrested, the judiciary may not countermand the decision by imposing “excessive” bail. When the legislature makes an offense non-bailable, or allows the imposition of high bail, the judicial branch may *357implement the decision without violating the Constitution.
The application of this rule to the implementation of statutes of the United States by federal courts makes perfect sense, for it carries out the original meaning of the language, the one we inherited from England. It is harder to apply the rule to state courts, because it assumes a separation of functions between legislature and judiciary that states need not employ. So far as federal courts are concerned, states may apportion governmental powers largely as they please. See City of Newport v. Iacobucci, — U.S. —, 107 S.Ct. 383, 385-86, 93 L.Ed.2d 334 (1986); Highland Farms Dairy, Inc. v. Agnew, 300 U.S. 608, 612, 57 S.Ct. 549, 551, 81 L.Ed. 835 (1937); Huggins v. Isenbarger, 798 F.2d 203, 207-08 (7th Cir.1986) (concurring opinion); United Beverage Co. of South Bend v. Indiana Alcoholic Beverage Commission, 760 F.2d 155 (7th Cir.1985). It is therefore doubtful that the eighth amendment, if “incorporated” and applied to states through the fourteenth, properly serves the separation-of-powers function it has when applied to cases in the federal courts. The Supreme Court has never hinted that the bail clause controls the allocation of powers within states — indeed, the Court has never held that it applies to the states. (This is still another question the sheriff did not present for decision.) Because of the differences in the allocation of functions, if the bail clause applies to the states at all, “errors” of state law by state courts are to be corrected by such processes (judicial and political) as the state makes available.
From time to time opinions of this court have put the question for decision as whether a state judge acted “arbitrarily” in setting bail. E.g., United States ex rel. Fitzgerald v. Jordan, 747 F.2d 1120, 1133 (7th Cir.1984). This may be taken as an invitation to review the record and measure the evidence against the standards of state law, as the district judge did. The constitutional question, though, is whether bail is “excessive” within the meaning of the eighth amendment. The purpose of the language, in Fitzgerald is not to set the district judge as an appellate tribunal over the supreme court of the state; it is a warning that the district court cannot and should not review the record in every case to make a de novo judgment of the “excessiveness” of the bail. Only if the choice is “arbitrary” — that is, only if it is way off the mark to conclude that a certain amount of bond is within the constitutional standard — may a federal court issue the writ. The search for “arbitrariness”, in other words, is designed to reduce the scope of federal review. This is how the court reads Fitzgerald today. The inquiry is like the one Jackson v. Virginia, 443 U.S. 307, 318-19, 99 S.Ct. 2781, 2788-89, 61 L.Ed.2d 560 (1979), employs to decide when evidence is constitutionally insufficient to support a conviction. We should ask: Could any reasonable judge believe that $607,000 was a constitutionally permissible bond for Garcia? If the bond is within the substantial range that a reasonable person could conclude falls short of “excessiveness”, the district court must decline to issue the writ.
The court does not pursue the lines of inquiry I have suggested, because the state did not ask us to. The sheriff wanted us to determine who was right, Judge Kowalski or Judge Shadur. The court properly confines the inquiry to questions preserved in the district court. The state has received the right answer to the question before us. I trust that this will not prevent the question from being recast in a future case.