opinion: Mr. Justice Brennan
  delivered the opinion of the Court.
  The question in this case is whether a State may make the defense of contributory negligence available to a railroad sued by a nonemployee for damages for personal injuries caused by the railroad’s failure to maintain its freight cars “with couplers coupling automatically by impact/’ as required by § 2 of the Federal Safety Appliance Act of 1893, 27 Stat. 531, 45 U. S. C. § 2.
  Petitioner was in the employ of Cargill, Inc., at its Cedar Rapids, Iowa, meal house and elevator on the line of respondent railroad. Petitioner’s duties were to move, weigh, and load freight cars spotted by respondent on Cargill’s siding track. He was working on the top of the third of a string of six cars when a coupler malfunctioned and caused the first two cars to break away. Petitioner dismounted and ran to the runaway cars. He climbed to the roof of one and was attempting to apply its brake when he fell 12 to 14 feet to a cement apron between the tracks and suffered severe injuries. He brought this action in tort in the Iowa District Court of Linn County. The only claim submitted to the jury was that petitioner’s injuries resulted from respondent’s maintenance, in violation of § 2, of a freight car with a defective coupler. Over petitioner’s objection the jury was instructed in accordance with settled Iowa tort law that it was petitioner’s burden “to establish by a preponderance or the greater weight of the evidence . . . that [he] was free from contributory-negligence,” defined as “negligence on the part of a person injured . . . which contributed in any way or in any degree directly to the injury.” The jury returned a verdict for respondent railroad. The Supreme Court of Iowa affirmed, - Iowa -, 160 N. W. 2d 838 (1968). We granted certiorari. 393 U. S. 1047 (1969). We affirm.
  The Safety Appliance Act did not create a federal cause of action for either employees or nonemployees seeking damages for injuries resulting from a railroad’s violation of the Act. Moore v. C. & O. R. Co., 291 U. S. 205 (1934). Congress did, however, subsequently provide a cause of action for employees: The cause of action created by the Federal Employers’ Liability Act of 1908, 35 Stat. 65, as amended, 45 U. S. C. § 51 et seq., embraces claims of an employee based on violations of the Safety Appliance Act. In such actions, the injured employee is required to prove only the statutory violation and thus is relieved of the burden of proving negligence, O’Donnell v. Elgin, J. & E. R. Co., 338 U. S. 384 (1949); Coray v. Southern Pac. R. Co., 335 U. S. 520 (1949); Affolder v. New York, C. & St. L. R. Co., 339 U. S. 96 (1950). He is not required to prove common-law proximate causation but only that his injury resulted “in whole or in part” from the railroad’s violation of the Act, 45 U. S. C. § 51; Rogers v. Missouri Pac. R. Co., 352 U. S. 500 (1957), and the railroad is deprived of the defenses of contributory negligence and assumption of risk, 45 U. S. C. §§ 53, 54.
  In contrast, the nonemployee must look for his remedy to a common-law action in tort, which is to say that he must sue in a state court, in the absence of diversity, to implement a state cause of action. Fairport, P. & E. R. Co. v. Meredith, 292 U. S. 589 (1934). “[T]he right to recover damages sustained . . . through the breach of duty sprang from the principle of the common law . . . and was left to be enforced accordingly . . . Moore v. C. & O. R. Co., supra, at 215. In consequence, we have consistently held that under the present statutory scheme the definition of causation and the availability of the defenses of assumption of risk and contributory negligence are left to state law. Schlemmer v. Buffalo, R. & P. R. Co., 220 U. S. 590 (1911); Fairport, P. & E. R. Co. v. Meredith, supra, at 598; Moore v. C. & O. R. Co., supra, at 215; Tipton v. Atchison, T. & S. F. R. Co., 298 U. S. 141 (1936). Our examination of the relevant legislative materials convinces us that this line of decisions should be reaffirmed.
  We recognize the injustice of denying recovery to a nonemployee which would not be denied to an employee performing the same task in the same manner as did petitioner. But it is for Congress to amend the statute to prevent such injustice. It is not permitted the Court to rewrite the statute.
  Affirmed.
  Section 2 of the Safety Appliance Act provides:
  “It shall be unlawful for any common carrier engaged in interstate commerce by railroad to haul or permit to be hauled or used on its line any car used in moving interstate traffic not equipped with couplers coupling automatically by impact, and which can be uncoupled without the necessity of men going between the ends of the cars.” 45 U. S. C. § 2.
  In addition to the Federal Safety Appliance Act and the Federal Employers’ Liability Act, see H. R. Rep. No. 1386, 60th Cong., 1st Sess., 6 (1908).
  See Louisell & Anderson, The Safety Appliance Act and the FELA: A Plea for Clarification, 18 Law & Contemp. Prob. 281 (1953).
instruction: What follows is an opinion from the Supreme Court of the United States. Your task is to determine the ideological "direction" of the decision ("liberal", "conservative", or "unspecifiable"). Use "unspecifiable" if the issue does not lend itself to a liberal or conservative description (e.g., a boundary dispute between two states, real property, wills and estates), or because no convention exists as to which is the liberal side and which is the conservative side (e.g., the legislative veto). Specification of the ideological direction comports with conventional usage. In the context of issues pertaining to criminal procedure, civil rights, First Amendment, due process, privacy, and attorneys, consider liberal to be pro-person accused or convicted of crime, or denied a jury trial, pro-civil liberties or civil rights claimant, especially those exercising less protected civil rights (e.g., homosexuality), pro-child or juvenile, pro-indigent pro-Indian, pro-affirmative action, pro-neutrality in establishment clause cases, pro-female in abortion, pro-underdog, anti-slavery, incorporation of foreign territories anti-government in the context of due process, except for takings clause cases where a pro-government, anti-owner vote is considered liberal except in criminal forfeiture cases or those where the taking is pro-business violation of due process by exercising jurisdiction over nonresident, pro-attorney or governmental official in non-liability cases, pro-accountability and/or anti-corruption in campaign spending pro-privacy vis-a-vis the 1st Amendment where the privacy invaded is that of mental incompetents, pro-disclosure in Freedom of Information Act issues except for employment and student records. In the context of issues pertaining to unions and economic activity, consider liberal to be pro-union except in union antitrust where liberal = pro-competition, pro-government, anti-business anti-employer, pro-competition, pro-injured person, pro-indigent, pro-small business vis-a-vis large business pro-state/anti-business in state tax cases, pro-debtor, pro-bankrupt, pro-Indian, pro-environmental protection, pro-economic underdog pro-consumer, pro-accountability in governmental corruption, pro-original grantee, purchaser, or occupant in state and territorial land claims anti-union member or employee vis-a-vis union, anti-union in union antitrust, anti-union in union or closed shop, pro-trial in arbitration. In the context of issues pertaining to judicial power, consider liberal to be pro-exercise of judicial power, pro-judicial "activism", pro-judicial review of administrative action. In the context of issues pertaining to federalism, consider liberal to be pro-federal power, pro-executive power in executive/congressional disputes, anti-state. In the context of issues pertaining to federal taxation, consider liberal to be pro-United States and conservative pro-taxpayer. In miscellaneous, consider conservative the incorporation of foreign territories and executive authority vis-a-vis congress or the states or judcial authority vis-a-vis state or federal legislative authority, and consider liberal legislative veto. In interstate relations and private law issues, consider unspecifiable in all cases.