opinion: Mr. Chief Justice Vinson
  delivered the opinion of the Court.
  The parties to this case are the same transit workers, the same transit company, and the Wisconsin Employment Relations Board before the Court in No. 329, decided this day, ante, p. 383. This action arises out of the same threatened strike discussed in that case. After a restraining order had led to postponement of the strike, the Wisconsin Board appointed arbitrators to “hear and determine” the dispute in accordance with the terms of the Wisconsin Public Utility Anti-Strike Law. Wis. Stat., 1949, § 111.55. Upon the filing of the arbitrators’ award, petitioners filed an action in a state circuit court to review that award. Id., § 111.60. That court affirmed the award and the Wisconsin Supreme Court affirmed, 257 Wis. 53, 42 N. W. 2d 477 (1950). We granted certiorari in this case together with No. 329, 340 U. S. 874 (1950).
  In the courts below and in this Court, petitioners attack the arbitration award on the same grounds urged against the Wisconsin Act as a whole in No. 329, and, in addition, raise issues peculiar to the arbitration phase of that act. But we do not reach these issues since it is clear that this case has become moot.
  The arbitration, award became effective on April 11, 1949. Under the Wisconsin Act, that award “shall continue effective for one year from that date,” unless sooner terminated by agreement of the parties. Wis. Stat., 1949, § 111.59. We are informed that this award was superseded by agreement, and, in any event, the one-year period has elapsed. There being no subject matter upon which the judgment of this Court can operate, the cause is moot.
  It is argued that the Wisconsin courts have adopted a practice of deciding questions of importance even though the case has become moot, and we are urged to follow that same practice. But whatever the practice in Wisconsin courts, “A federal court is without power to decide moot questions or to give advisory opinions which cannot affect the rights of the litigants in the case before it. United States v. Alaska S. S. Co., 253 U. S. 113, 115-16, and cases cited; United States v. Hamburg-American Co., 239 U. S. 466, 475-77.” St. Pierre v. United States, 319 U. S. 41, 42 (1943).
  It appearing that the cause has become moot, the judgment of the Supreme Court of Wisconsin is vacated without costs and the cause is remanded for such proceedings as by that court may be deemed appropriate.
  It is so ordered.
  It has also been argued that No. 329 and No. 438 are moot by reason of the settlement of the immediate dispute which led to the strike action in each case. The injunction before us in No. 329 is "perpetual” by its terms so that the action does not become moot even though the decree be obeyed. J. I. Case Co. v. Labor Board, 321 U. S. 332, 334 (1944); Federal Trade Comm’n v. Goodyear Tire & Rubber Co., 304 U. S. 257, 260 (1938), and cases cited therein. As to No. 438, the judgment below imposes fines upon petitioners. No question of mootness can be raised so long as enforcement of that judgment is sought.
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.