THE CASE OF GELPCKE v. DUBUQUE, 315 ing its own decision.^ And, finally, it was long ago intimated that a United States court would not follow the State decisions where these were regarded as biased, and unjust to citizens of other States. It will easily appear that in some sense and to some extent there should be a recognition of such a principle as the one just named; all State courts must keep within the line of reason in order to make it just that the United States courts should follow them. Yet, notwithstanding all these qualifications, it is still true, and is recognized as the sound general principle in the class of cases now under discussion, that the courts of the United States will follow the decisions of the State courts in ascertaining and con- struing their own law. The declarations to this effect are many and emphatic.^ It is with one of the qualifications of this rule that we are con- cerned in this case, namely, the one arising out of the danger to citizens of other States from local prejudice. I have said that some power of varying from the decisions of the States must necessarily exist, as regards this sort of case, that, at least, the local courts must keep within the limits of reason. Shall the range of the United States court, in differing from the local tribunals, go farther than that, and how much farther? In Rowan v. Runnels, 5 How. 139 (a case coming up from the Circuit Court of the United States for Mississippi), Chief Justice Taney remarks: We ought not to give to them [the decisions of State courts] a retroactive effect, and allow them to render invalid contracts entered into with citizens of other States, which in the judgment of this court were lawfully made. For if such a rule were adopted . . . it is evident that the provision in the Constitu- tion of the United States which secures to the citizens of another State the right to sue in the courts of the United States, might be- come utterly useless and nugatory." This is the assertion of a right, which is, indeed, an obvious one, to depart from the State court's construction of the local law, in so far as is necessary to prevent the annulling of that protection for citizens of other States which the Constitution was intended to secure. For, although the courts of the United States in this sort of case have to apply the ^ Shelby v. Guy, 11 Wheat. 361. ^ Elmendorf v. Taylor, 10 Wheat. 152, 159-60; Webster v. Cooper, 14 How. 488, 502-5; Nesmith v. Sheldon, 7 How. 812; Williamson v. Berry, 8 How. 495, 558; Lefl&ngwell v. Warren, 2 Black, 599.
