delivered the opinion of the Court.

The question for decision is whether the oft-challenged doctrine of Swift v. Tyson^[1] shall now be disapproved.

Tompkins, a citizen of Pennsylvania, was injured on a dark night by a passing freight train of the Erie Railroad Company while walking along its right of way at Hughestown in that State. He claimed that the,accident occurred through negligence in the operation, or maintenance, of the train; that h.e was rightfully on the premises as licensee because on a commonly used beaten: footpath which rah for a short distance alongside the tracks; and that he was struck by something which looked like a door projecting from one of the moving cars. To enforce that claim he brought an action in the federal court for southern New York, which had jurisdiction because the company is a corporation of that State. It denied liability; and the case was tried by a jury.

[*70] The Erie insisted that its duty to Tompkins was no greater than that , owed to a trespasser. It contended, among other things, that its duty to Tompkins, and hence its liability, should be determined in accordance with the Pennsylvania law;,that under the law of Pennsylvania, as declared by its highest' court, persons who use pathways along the railroad right of way — that is a longitudinal pathway as distinguished from a crossing — are to be deemed trespassers; and that the railroad is not liable for injuries to undiscovered trespassers resulting from its negligence, unless it be wanton or wilful. Tompkins denied that any such rule had been established by the decisions of the Pennsylvania courts; and contended that, since there was no statute of the State on the subject, the railroad’s duty and liability is to be determined in federal courts as a matter of general law.

.. The trial judge refused to rule that the applicable law precluded recovery. The jury brought in a verdict of $30,000; and the judgment entered thereon was affirmed by the Circuit Court of Appeals, which held, 90 F. 2d 603, 604, that it was unnecessary to consider whether the law of Pennsylvania was. as contended, because the question was one not of local, but of general, law and that “upon questions of general law the federal courts are free, in the absence of a local statute, to exercise their independent judgment as to what the law is; and it is well settled that the question of the responsibility of a railroad for injuries caused by its servants is one of general law. . . . Where the public has made open and notorious use of a railroad right of way for a long period of time and without objection, the company owes to persons on such permissive pathway a duty of care in the operation of its trains. ... It is likewise generally recognized law that a jury may find that negligence exists toward a pedestrian using a permissive path on the railroad right of way if he is hit by some object projecting from the side of the train.”

[*71] The Erie had contended that application of the Pennsylvania rule was required, among other things, by § 34 of the Federal Judiciary Act of September 24, 1789, c. 20, 28 U. S. C. § 725, which provides:

“The laws of the several States, except where the Constitution, treaties, or statutes of the -United States otherwise require or provide, shall be regarded as rules of decision in trials at common law, in the courts of the United States, in cases where they apply.”

Because of the importance of the question whether the federal court was .free to disregard the alleged rule of the Pennsylvania common law, we granted certiorari.

First. Swift v. Tyson, 16 Pet. 1, 18, held that federal courts exercising jurisdiction on the ground of diversity of citizenship need not, in matters of general jurisprudence, apply the unwritten law of the State as declared by .its highest court; that they are free to exercise an independent judgment as to what the common law of the State is — or should be; and that, as there stated by Mr. Justice Story:

“the true interpretation of the thirty-fourth section limited its application to state laws strictly local, that is to say, to the positive statutes of the state, and the construction thereof adopted by the local tribunals, and to rights and titles to things having a permanent locality, such as the rights and titles to real estate, and other matters immovable and intraterritorial in their nature and character. It never has been supposed by us, that the section did apply, or was intended to apply, to questions of a more general nature, not at all dependent upon local statutes or local usages of a fixed and permanent operation, as, for example, to the construction of ordinary contracts or other written instruments, and especially to questions of general commerbial law, where the state tribunals are called upon to perform the like functions as ourselves, that is, to' ascertain upon general reasoning and legal analogies, what is the true exposition of the contract or[*72] instrument, or what is the just rule furnished by the principles of commercial law to govern the case.”

The Court in applying the rule of § 34 to equity cases, in Mason v. United States, 260 U. S. 545, 559, said: “The statute, however, is merely declarative of the rule which would exist in the absence of the statute.” ^[2] The federal courts assumed, in' the broad field of “general law,” the power to declare rules of decision which Congress was confessedly without power to enact as statutes. Doubt was repeatedly expressed as'to the correctness of the construction given § 34,^[3] and as to the soundness of the rule which it introduced.^[4] But it was the more recent research of a competent scholar, who . examined the original document, which established that the construction given to it by the Court was erroneous; and that the purpose of the section was merely to make certain that, in all matters except those in which some federal law is controlling,[*73] the federal courts exercising jurisdiction in diversity of citizenship cases would apply as their rules of decision the law of the State, unwritten as well as written.^[5]

Criticism of the doctrine became widespread after the decision of Black & White Taxicab Co. v. Brown & Yellow Taxicab Co., 276 U. S. 518.^[6] There, Brown and Yellow, a Kentucky corporation owned by Kentuckians, and the Louisville and Nashville Railroad, also a Kentucky corporation, wished that the former should have the exclusive privilege of soliciting passenger and baggage transportation at the Bowling Green, Kentucky, railroad station; and that the Black and White, a competing Kentucky corporation, should be prevented from interfering with that privilege. Knowing that such a contract would be void under the common law of Kentucky, it was arranged that the Brown and Yellow reincorporate under the law of Tennessee, and that the contract with the railroad should be executed there. The suit was then brought by the Tennessee corporation in the federal court for western Kentucky to enjoin competition by the Black and White; an injunction issued by the District Court[*74] waa sustained lay the Court of Appeals; and this Court, citing many decisions in which the doctrine of Swift v. Tyson had been applied, affirmed the decree.

Second. Experience in applying the doctrine of Swift v. Tyson, had revealed its defects, political and social; and the benefits expected to flow from the rule did not accrue. Persistence of state courts in their own opinions on questions of common law prevented uniformity;^[7] and the . impossibility of discovering a satisfactory line of demarcation between the province of general law and that of local law developed a new well of uncertainties.^[8]

On the other, hand, the mischievous results of the doctrine had becoihe apparent: Diversity of citizenship jurisdiction was conferred in order to prevent apprehended discrimination in state courts against those not citizens of the State. Swift v. Tyson introduced grave discrimination ’by non-citizens against citizens. It made rights enjoyed under the unwritten “general law” vary according to whether enforcement was sought in the state[*75] or in the federal court; and the privilege of selecting the court in which the right should be determined was conferred upon the non-citizen.^[9] Thus, the doctrine rendered impossible equal protection of the law. In attempting to promote uniformity of law throughout the United States^ the doctrine had prevented uniformity in the administration of the law of the State.

The discrimination resulting became in practice far-reaching. This resulted in part from the broad province accorded to the so-called “general law” as to which federal courts exercised an independent judgment.^[10] In addition to questions of purely commercial law, “general law” was held to include the obligations under'contracts entered into and to be performed within the State,^[11] the extent to which a carrier operating within a State may stipulate for exemption from liability for his own negligence -or that of his employee;^[12] the liability for torts committed within the State upon persons resident or property located there, even where the question of liar[*76] bility depended upon the scope of a property right conferred by the State;^[13] and the right to exemplary or punitive damages.^[14] Furthermore, state decisions construing local deeds,^[15] mineral conveyances,^[16] and even devises of real estate^[17] were disregarded.^[18]

In part the discrimination resulted from the wide range of persons held entitled to avail themselves of the federal rule by resort to the diversity of citizenship jurisdiction. Through this jurisdiction individual citizens willing to remove from their own State and' become citizens of another might avail themselves of the federal rule.^[19] And, without even change of residence, a corporate citizen of[*77] the State could avail itself of the federal rule by re-incorporating under the laws of another State, as was done in the Taxicab case.

The injustice and confusion incident to the doctrine of Swift v. Tyson have been repeatedly urged as reasons for abolishing or limiting diversity of citizenship jurisdiction.^[20] Other legislative relief has been proposed.^[21] If only a question of statutory construction were involved, we should not be prepared to abandon a doctrine so widely applied throughout nearly a century.^[22] But the uncon[*78]stitutionality of the course pursued has now been made clear and compels us to do so.

Third. Except in matters governed by the Federal Constitution or by Acts of Congress, the law to be applied in any case is the law of the State. And whether the law of the State shall be declared by its Legislature in a statute or by its highest court in a decision is not a matter of federal concern. There is no federal general common law. Congress has no power to declare substantive rules of common law applicable in a State whether they be local in their nature or “general,” be they commercial law or a part of the law of torts. And no clause-in the Constitution purports to confer such a power upon the federal courts. As stated by Mr. Justice Field when protesting in Baltimore & Ohio R. Co. v. Baugh, 149 U. S. 368, 401, against ignoring the Ohio common law of fellow servant liability:

“I am aware that what has been termed the general law of the country — which is often little less than what the judge advancing the doctrine thinks at the time should be the general law on a particular subject — has been often advanced in judicial opinions of this court to control a . conflicting law of a State., I admit that learned judges have fallen into the habit^[1] of-repeating this doctrine as a convenient mode of brushing aside the law of a State in conflict with their views. And I confess that, moved and governed by the authority of the great names of those judges, I have, myself, in many instances, unhesitatingly and confidently, but I think now-erroneously, repeated the same doctrine. But, notwithstanding the great names which may be cited in favor of the doctrine, and notwithstanding the frequency with which the doctrine has been reiterated, there stands, as a perpetual protest against its repetition, the Constitution of the United States, which recognizes and preserves the autonomy and independence , of the States — independence in their legislative and inde[*79]pendence in their judicial departments. Supervision over either the legislative or the judicial action of the States is in no case permissible except as to matters by the Constitution specifically authorized or delegated to the United States. Any interference with either, except as thus permitted, is an invasion of the authority of the State and, to that extent, a denial of its independence.”

The fallacy underlying the rule declared in Swift v. Tyson is made clear by Mr. Justice Holmes.^[23] The doctrine rests upon the assumption that there is “a transcendental body of law outside of any particular State but obligatory within it unless and until changed by statute,” that federal courts have the power to use their judgment as to what the rules of common law are; and that in the federal courts “the parties are entitled to an independent judgment on matters of general law "—:

“but law in the sense in which courts speak of it today does not exist without some definite authority behind it. The common law so far as it is enforced in a State, whether called common law or not, is not the common law generally but the law of that State existing by the authority of that State without regard to what it may .have been in England or anywhere else. . . .

“the authority and only authority is the State, and if that be so, the voice adopted by the State as its own [whether it be of its Legislature or of its Supremé Court] should utter the last word.”

Thus the doctrine of Swift v. Tyson is, as Mr. Justice Holmes said, “an unconstitutional assumption of powers by courts of the United States which no lapse of time or respectable array of opinion should make us hesitate to correct.” In disapproving that doctrine we do not hold[*80] unconstitutional § 34 of the Federal Judiciary Act of 1789 or any other Act of Congress. We merely declare that in applying the doctrine this Court and the lower courts have invaded rights whicíi in our opinion are reserved by the Constitution to the several States.

Fourth. The defendant contended that by the common law of Pennsylvania as declared by its highest court in Falchetti v. Pennsylvania R. Co., 307 Pa. 203; 160 A. 859, the only duty owed to the plaintiff was to refrain from wilful or wanton injury. The plaintiff denied that such is the Pennsylvania law.^[24] In support of their respective contentions the parties discussed and cited many decisions of the Supreme Court of the State. The Circuit Court of Appeals ruled that the question of liability is one of general law; and on thjat ground declined to decide the issue of state law. As. we hold this was error, the judgment is reversed and the case remanded to it for further proceedings in conformity with our opinion.

Reversed.

The case presented by the evidence is a simple one. Plaintiff was severely injured in Pennsylvania. While walking on defendant’s right of way along a much-used path at the end of the cross ties of its main track, he came into collision with an open door swinging from the side of a car in a train going in the opposite direction. Having been warned by whistle and headlight, he saw the locomo[*81]tive approaching and had time and space enough to step aside and so avoid danger. To justify his failure to get out of the way, he says that upon many other occasions he had safely walked there while trains'passed.

Invoking jurisdiction on the ground of. diversity of citizenship, plaintiff, a citizen .and resident of Pennsylvania, brought this suit to recover damages against, defendant, a New York corporation, in the federal court for the southern district of that State. The issues were whether negligence of defendant was a proximate cause of his injuries and whether negligence of plaintiff contributed. He claimed that, by hauling the car with the open door, defendant violated a duty to him. The defendant insisted that it violated no duty and that plaintiff’s injuries were caused by his own negligence. ..The jury gave him a verdict on which the trial court entered judgment; the circuit court of appeals affirmed. 90 F. (2d) 603.

Defendant maintained, citing Falchetti v. Pennsylvania R. Co., 307 Pa. 203; 160 A. 859, and Koontz v. B. & O. R. Co., 309 Pa. 122; 163 A. 212, that the only duty owed plaintiff was to refrain from willfully or wantonly injuring him; it argued that the courts of Pennsylvania had so ruled with respect to persons using a customary longitudinal path, as distinguished from one crossing the track. The plaintiff, insisted that the Pennsylvania decisions did not establish the rule for which the defendant contended.. Upon that issue the circuit court of appeals said (p. 604): “We need hot go into this' matter since the defendant concedes that the great weight of authority in other states is' to the contrary.- This concession is fatal to its contention, for upon questions of general law the federal courts are. free, in absence of a local statute, to exercise their independent judgment as to what the law is; and it is well settled that the question of the responsibility of a railroad for injuries caused by its servants is one of general law.”[*82] Upon that basis the court held the evidence sufficient to sustain a finding that plaintiff’s injuries were caused by the negligence of defendant. It also held the question of contributory negligence one for the jury.

Defendant’s petition for writ of certiorari presented two questions: Whether its duty toward plaintiff should have been determined in accordance with the law as found by the highest court of Pennsylvania, and whether the evidence conclusively showed plaintiff guilty of contributory negligence. Plaintiff contends that, as always heretofore held by this Court, the issues of negligence and contributory negligence are to be determined by general law against which local decisions may not be held conclusive; that defendant relies.on a solitary Pennsylvania case of doubtful applicability and that, even jtf the decisions of'the courts of that State were deemed controlling, the same result would have to be reached.

No constitutional question was suggested or argued below or here. And as a general rule, this Court will not consider any question not raised below and presented by the petition. Olson v. United States, 292 U. S. 246, 262. Johnson v. Manhattan Ry. Co., 289 U. S. 479, 494. Gunning v. Cooley, 281 U. S. 90, 98. Here it does not decide either of the questions presented but, changing the rule of decision in force since the foundation of the Government, remands the case td be adjudged according to a standard never before deemed permissible.

The opinion just announced states that “the question for decision is whether the oft-challenged doctrine of Swift v. Tyson [1842, 16 Pet. 1] shall now be disapproved.”

That case involved the construction of the Judiciary Act of 1789, § 34: “The laws of the several states, except where the Constitution, treaties, or statutes of the. United States otherwise require or provide, shall be regarded as rules of decision in trials at common law in the courts of-[*83]the United States in cases where they apply.” Expressing the view of all the members of the Court, Mr. Justice Story said (p. 18): “In the ordinary use of language it will hardly be contended that the decisions of Courts constitute laws. They are, at most, only evidence of what- the laws are, and not. of themselves laws. They are often re-examined, reversed, and qualified by the Courts themselves, whenevér they are found to be either defective, or ill-founded, or otherwise incorrect. The laws of a -state are more usually understood to mean, the rules and enactments promulgated by the legislative authority thereof, or long established local customs having the force of laws. In all the various cases, which have hitherto come before us for decision, this Court have uniformly supposed, that the true interpretation of the thirty-fourth section limited its application to state laws strictly local, that is to say, to the positive statutes of the state, and the construction thereof adopted by the local tribunals, and to rights and titles' to things having a permanent locality, such as the rights and titles to' real- estate, and other matters immovable and intraterritorial in their nature and character. It never has been supposed by us, that the section did apply, or was designed to apply, to questions of a more general nature, not at all dependent upon local statutes or local usages of a fixed and permanent operation, as, for example, to the construction of ordinary contracts or other written instruments, and especially to questions of general commercial law, where the state .tribunals are called upon'to perform the like functions as ourselves, that is, to ascertain upon general reasoning and legal analogies, what is the true exposition of the contract or instrument, or what is the just rule furnished by the prin-. ciples of commercial law to govern the case. And we have not now the slightest difficulty in holding., that this section, upon its true intendment and construction, is strictly limited to local statutes and local usages of the .character[*84] before stated, and does not extend to contracts and other instruments of a commercial nature, the true interpretation and effect whereof are to be sought, not in the decisions of the local tribunals, but in the general principles and doctrines of commercial jurisprudence. Undoubtedly, the decisions of the local tribunals upon such subjects are entitled to, and will receive, the most deliberate attention and respect of this Court; but they cannot furnish positive rules, or conclusive authority, by which our own judgments are to be bound up and governed.” (Italics added.)

The doctrine of that case has been followed by this Court in an unbroken line of decisions. So far as appears, it was not questioned until more than 50 years later, and then by a single judge.^[1] Baltimore & Ohio R. Co. v. Baugh, 149 U. S. 368, 390. In that case, Mr. Justice Brewer, speaking for the Court, truly said (p. 373): “Whatever differences of opinion may have been expressed, have not been on the question whether a matter of general law should be settled by the independent judgment of this court, rather than through an adherence to the decisions of the state courts, but upon the other question, whether a given matter is one of local or of general law.”

And since that decision, the division of opinion in this Court has been one of the same character as it was before. In 1910, Mr. Justice Holmes, speaking for himself and two other Justices, dissented from the holding that a[*85] court of the United States was bound to exercise its own independent judgment in the construction of a conveyance made before the state courts had rendered an authoritative decision as to its meaning and effect. Kuhn v. Fairmont Coal Co., 215 U. S. 349. But that dissent accepted (p. 371) as ‘‘settled” the doctrine of Swift v. Tyson, and insisted (p. 372) merely that the case under consideration was by nature and necessity peculiarly local.

Thereafter, as before, the doctrine was constantly applied.^[2] In Black & White Taxicab Co. v. Brown & Yellow Taxicab Co., 276 U. S. 518, three judges dissented. The writer of the dissent, Mr. Justice Holmes, said, however (p. 535): “I should leave Swift v. Tyson undisturbed, as I indicated in Kuhn v. Fairmont Coal Co., but I would not allow it to spread the assumed dominion into new fields.”

No more unqualified application of the doctrine can be found than in decisions of this Court speaking through Mr. Justice Holmes. United Zinc Co. v. Britt, 258 U. S. 268. Baltimore & Ohio R. Co. v. Goodman, 275 U. S. 66, 70. Without in the slightest departing from that doctrine, but implicitly applying it, the strictnéss of the rule laid down in the Goodman case was somewhat ameliorated by Pokora v. Wabash Ry. Co., 292 U. S. 98.

Whenever possible, consistently with standards sustained by reason and authority constituting the general, law, this Court has followed applicable decisions of state courts. Mutual Life Ins. Co. v. Johnson, 293 U. S. 335, 339. See Burgess v. Seligman, 107 U. S. 20, 34. Black & White Taxicab Co. v. Brown & Yellow Taxicab Co., supra, 530. Unquestionably the issues off negligence and contributory negligence upon which decision of this case[*86] depends are questions of general law. Hough v. Railway Co., 100 U. S. 213, 226. Lake, Shore & M. S. Ry. Co. v. Prentice, 147 U. S. 101. Baltimore & Ohio R. Co. v. Baugh, supra. Gardner v. Michigan Central R. Co., 150 U. S. 349, 358. Central Vermont Ry. Co. v. White, 238 U. S. 507, 512. Baltimore & Ohio R. Co. v. Goodman, supra. Pokora v. Wabash Ry. Co., supra.

While amendments to § 34 have from time to time been suggested, the section., stands as originally enacted. Evidently Congress has intended throughout the years that the rule of decision as construed should continue to govern federal courts in trials at common law. The opinion just announced suggests that Mr. Warren’s research has established that from the beginning this Court has erroneously construed § 34. But that author’s “New Light on the History of the Federal Judiciary Act of 1789” does not purport to be authoritative and was intended to be no more than suggestive. The .weight to be given to his discovery has never been discussed at this bar. Nor does the. opinion indicate the ground, disclosed by the research. In his dissenting opinion in the Taxicab case, Mr. Justice Holmes referred to Mr., barren’s work but failed to persuade the Court that “laws” as used in § 34 included varying and possibly ill-considered rulings by the courts of á State on questions of. common law. See, e. g., Swift v. Tyson, supra, 16-17. It well may be that, if the Court should now call for argument of counsel on the basis of Mr. Warren’s research, it would adhere to the construction it has always put upon § 34-. Indeed, the opinion in this case so indicates. For it declares: “If only a question of statutory construction were involved, we should not be prepared to abandon a doctrine so widely applied throughout a century. But the unconstitutionality of the course pursued has now been made clear and compels us to do so.” This means that, so far as concerns the rule of decision now condemned, the Judiciary Act of 1789, passed to establish judicial[*87] courts to exert the judicial power of the United States, and especially § 34 of that Act as construed, is unconstitutional; that federal courts are now bound to follow decisions of the courts of the State in which the controversies arise; and that Congress is powerless otherwise to ordain. It is hard to foresee the consequences of the radical change so made. Our opinion in the Taxicab case cites numerous decisions of this Court which serve in part to indicate the field from which it is now intended forever to bar the federal courts. It extends to all matters of contracts and torts not positively governed by state enactments. Counsel searching for precedent and reasoning to disclose common-law principles on which to guide clients and conduct litigation are by this decision told that as to all of these questions the decisions of this Court and other federal courts are no longer anywhere authoritative.

This Court has often emphasized its reluctance to consider constitutional questions, and that legislation will not be held invalid as repugnant to the fundamental law if the case may be decided upon any other ground. In view of grave consequences liable to result from erroneous exertion of its power to set aside legislation, the Court should move cautiously, seek assistance of counsel, act only after ample deliberation, show that the question is before the Court, that its decision cannot be avoided by construction of the statute assailed or otherwise, indicate precisely the principle or provision of the Constitution held to have been transgressed, and fully disclose. the reasons and authorities found to warrant the conclusion of invalidity. These safeguards against the improvident use of the great power to invalidate legislation are so well-grounded and familiar that statement of reasons or citation of authority to support them is no longer necessary. But see e. g.: Charles River Bridge v. Warren Bridge, 11 Pet. 420, 553; Township of Pine Grove v. Talcott, 19 Wall. 666, 673; Chicago & G. T. Ry. Co. v. Wellman, 143 U. S. 339, 345;[*88] Baker v. Grice, 169 U. S. 284, 292; Martin v. District of Columbia, 205 U. S. 135, 140.

So far as appears, no litigant has ever challenged the power of Congress to establish the: rule as construed. It has so long endured that its destruction now without appropriate deliberation cannot be justified. There is nothing in the opinion to suggest that consideration of any constitutional question is necessary to a decision of the case. By way of reasoning, it contains nothing that requires the conclusion reached. Admittedly,- there is no authority to support that conclusion. Against the protest of those joining in this opinion, the Court declines to assign the case for reargument. It may not justly be assumed that the labor and argument of counsel for the parties would not disclose the right conclusion and aid the Court in the statement of reasons to support it. Indeed, it would have been appropriate to give Congress opportunity to be heard before devesting it of power to prescribe rules of decision to be followed' in the courts of the United States. See Myers v. United States, 272 U. S. 52, 176.

The course pursued by the Court in this case is repugnant to the Act of Congress of August 24, 1937, 50 Stat. 751. It declares: “That whenever the constitutionality of any Act of Congress affecting the public interest is drawn in question in any court of the United States in any suit or proceeding to which the United States, or any agency thereof, or any officer or employee thereof, as such officer or employee, is not a party, the court having jurisdiction of the suit or proceeding shall certify such fact to the Attorney General. In any such case the court shall permit the United States to intervene and become á party for presentation of evidence (if evidence is otherwise receivable in such suit or proceeding) and argument upon the question of the constitutionality of such Act.. .In any such suit or proceeding the United States shall, subject to the applicable provisions of law, have all the rights of a.[*89] party and the liabilities of a party as to court costs to the extent necessary for a proper presentation of the facts and law relating to the constitutionality of such Act.” That provision extends to this Court. § 5. If defendant had applied for and obtained the writ of certiorari upon the claim that, as now’ held, Congress has no power to prescribe the rule of decision, § 34 as construed, it would have been the duty of thi^ Court to issue the prescribed certificate to the Attorney General in order that the United States might intervene and be heard on .the constitutional question. Within the purpose of the statute and its true intent and meaning, the constitutionality of that measure has been “drawn in question.” Congress intended to give the United States the right to be heard in every case involving constitutionality of an Act affecting ihe public interest. In view of the rule that, in the absence of chállenge of constitutionality, statutes will not here be invalidated on that ground, the Act of August 24, 1937 extends to cases where constitutionality is first “drawn’ in question” by the Court. No extraordinary or-unusual action by the Court after submission of the cause should be permitted to frustrate the wholesome purpose of that Act. The duty it imposes ought here to be willingly assumed. If it were doubtful whether this case is within the scope of the Act, the Court should give the United States opportunity to intervene and, if so advised, to present argument on the constitutional question, for undoubtedly it is one of great public importance. That would be to construe the Act according to its meaning.

The Court’s opinion in its first sentence defines the question to be whether the doctrine of Swift v. Tyson shall now be disapproved; it recites (p. 72) that Congress is without power to prescribe rules of decision that have been followed by federal courts as s, result of the construction of § 34 in Swift v. Tyson and since; after discussion, it declares (pp. 77-78) that “the unconstitutionality of the course pursued [meanin the rule of decision[*90] resulting from that construction] compels" abandonment of the doctrine so long applied; and then near the end' of the last page the Court states that it does not hold § 34 unconstitutional, but merely that, in applying the doctrine of Swift v. Tyson construing it, this Court and the lower courts have invaded rights which are reserved by the Constitution to the several States. But, plainly through the form of words employed, the substance of the decision appears; it strikes down as unconstitutional § 34 as construed by our decisions; it divests the Congress of power to prescribe rules to be followed by federal courts when deciding questions of general law. In that broad field it compels this and the lower federal courts to follow decisions of the courts of a particular State.

I am of opinion that the constitutional validity of the rule need not be considered, because under the law, as found by the courts of Pennsylvania and -generally throughout the country, it is plain that the evidence required a finding that plaintiff was guilty of negligence that contributed to cause his injuries and that the judgment below should be reversed upon that ground.