What follows is an opinion from the Supreme Court of the United States. Your task is to determine the bases on which the Supreme Court rested its decision with regard to the legal provision that the Court considered in the case. Consider "judicial review (national level)" if the majority determined the constitutionality of some action taken by some unit or official of the federal government, including an interstate compact. Consider "judicial review (state level)" if the majority determined the constitutionality of some action taken by some unit or official of a state or local government. Consider "statutory construction" for cases where the majority interpret a federal statute, treaty, or court rule; if the Court interprets a federal statute governing the powers or jurisdiction of a federal court; if the Court construes a state law as incompatible with a federal law; or if an administrative official interprets a federal statute. Do not consider "statutory construction" where an administrative agency or official acts "pursuant to" a statute, unless the Court interprets the statute to determine if administrative action is proper. Consider "interpretation of administrative regulation or rule, or executive order" if the majority treats federal administrative action in arriving at its decision.Consider "diversity jurisdiction" if the majority said in approximately so many words that under its diversity jurisdiction it is interpreting state law. Consider "federal common law" if the majority indicate that it used a judge-made "doctrine" or "rule; if the Court without more merely specifies the disposition the Court has made of the case and cites one or more of its own previously decided cases unless the citation is qualified by the word "see."; if the case concerns admiralty or maritime law, or some other aspect of the law of nations other than a treaty; if the case concerns the retroactive application of a constitutional provision or a previous decision of the Court; if the case concerns an exclusionary rule, the harmless error rule (though not the statute), the abstention doctrine, comity, res judicata, or collateral estoppel; or if the case concerns a "rule" or "doctrine" that is not specified as related to or connected with a constitutional or statutory provision. Consider "Supreme Court supervision of lower federal or state courts or original jurisdiction" otherwise (i.e., the residual code); for issues pertaining to non-statutorily based Judicial Power topics; for cases arising under the Court's original jurisdiction; in cases in which the Court denied or dismissed the petition for review or where the decision of a lower court is affirmed by a tie vote; or in workers' compensation litigation involving statutory interpretation and, in addition, a discussion of jury determination and/or the sufficiency of the evidence.

Opinion:
UNITED STEELWORKERS OF AMERICA v. ENTERPRISE WHEEL & CAR CORP.
No. 538.
Argued April 28, 1960.
Decided June 20, 1960.
Elliot Bredhoff and David E. Feller argued the cause for petitioner. With them on the brief were Arthur J. Goldberg, James P. Clowes and Carney M. Layne.
William C. Beatty argued the cause for respondent. With him on the brief was Jackson N. Huddleston.
Opinion of the Court by
Mr. Justice Douglas,
announced by Mr. Justice Brennan.
Petitioner union and respondent during the period relevant here had a collective bargaining agreement which provided that any differences “as to the meaning and application” of the agreement should be submitted to arbitration and that the arbitrator’s decision “shall be final and binding on the parties.” Special provisions were included concerning the suspension and discharge of employees. The agreement stated:
“Should it be determined by the Company or by an arbitrator in accordance with the grievance procedure that the employee has been suspended unjustly or discharged in violation of the provisions of this Agreement, the Company shall reinstate the employee and pay full, compensation at the employee’s regular rate of pay for the time lost.”
The agreement also provided:
. . It is understood and agreed that neither party will institute civil suits or legal proceedings against the other for alleged violation of any of the provisions of this labor contract; instead all disputes will be settled in the manner outlined in this Article III — Adjustment of Grievances.”
A group of employees left their jobs in protest against the discharge of one employee. A union official advised them at once to return to work. An official of respondent at their request gave them permission and then rescinded, it. The next day they were told they did not have a job any more “until this thing was settled one way or the other.”
• A grievance was filed; and when respondent finally refused to arbitrate^ this suit was brought for specific enforcement of the arbitration provisions of the agreement. The District Court ordered arbitration. The arbitrator found that the discharge of the men was not justified, though their conduct, he said, was improper. In his view the facts warranted at most a suspension of the men for 10 days each. After their discharge and before the arbitration award the collective bargaining agreement had expired. The union, however, continued to represent the workers at the plant. The arbitrator rejected the contention that expiration of the agreement barred reinstatement of the employees. He held that the provision of the agreement above quoted imposed an unconditional obligation on the employer. He awarded reinstatement with back pay, minus pay for a 10-day suspension and such sums as these employees received from other employment.
Respondent refused to comply with the award. Petitioner moved the District Court for enforcement. The District Court directed respondent to comply. 168 F. Supp. 308. The Court of Appeals, while agreeing that the District Court had jurisdiction to enforce an arbitration award under a collective bargaining agreement, held that the failure of the award to specify the amounts to be deducted from the back pay rendered the award unenforceable. That defect, it agreed, could be remedied by requiring the parties to complete the arbitration. It went on to hold, however, that an award for back pay subsequent to the date of termination of the collective bargaining agreement could not be enforced. It also held that the requirement for reinstatement of the discharged employees was likewise unenforceable because the collective bargaining agreement had expired. 269 F. 2d 327. We granted certiorari. 361 U. S. 929.
The refusal of courts to review the merits of an arbitration award is the proper approach to arbitration under collective bargaining agreements. The federal policy of settling labor disputes by arbitration would be undermined if courts had the final say on the merits of the awards. As we stated in United Steelworkers of America v. Warrior & Gulf Navigation Co., ante, p. 574, decided this day, the arbitrators under these collective agreements are indispensable agencies in a continuous collective bargaining'process. They sit to settle disputes at the plant level — disputes that require for their solution knowledge of the custom and practices of a particular factory or of a particular industry as reflected in particular agreements.
When an arbitrator is commissioned to interpret and apply the collective bargaining agreement, he is to bring his informed judgment to bear in order to reach a fair solution of a problem. This is especially true when it comes to formulating remedies. There the need is for flexibility in meeting a wide variety of situations. The draftsmen may never have thought of what specific remedy should be awarded to meet a particular contingency. Nevertheless, an arbitrator is confined to interpretation and application of the collective bargaining agreement; he does not sit to dispense his own brand of industrial justice. He may of course look for guidance from many sources, yet his award is legitimate only so long as it draws its essence from the collective bargaining agreement. When the arbitrator's words' manifest an infidelity to this obligation, courts have no choice but to refuse enforcement of the award.
The opinion of the arbitrator in this case, as it bears upon the award of back pay beyond the date of the agreement's expiration and reinstatement, is ambiguous. It may be read as based solely upon the arbitrator's view of the requirements of enacted legislation, which would mean that he exceeded the scope of the submission. Or it may be read as embodying a construction of the agreement itself, perhaps with the arbitrator looking to “the law” for help in determining the sense of the agreement. A mere ambiguity in the opinion accompanying an award, which permits the inference that the arbitrator may have exceeded his authority, is not a reason for refusing to enforce the award. Arbitrators have no obligation to the court to give their reasons for an award. To reqhire opinions free of ambiguity may lead arbitrators to play it safe by writing no supporting opinions. This would be undesirable for a well-reasoned opinion tends to engender confidence in the integrity of the process and aids in clarifying the underlying agreement. Moreover, we see no reason to assume that this arbitrator has abused the trust the parties confided in him and has not stayed within the areas marked out for his consideration. It is not apparent that he went beyond the submission. The Court of Appeals’ opinion refusing to enforce the reinstatement and partial back pay portions of the award was not based upon any finding that the arbitrator did not premise his award on his construction of the contract. It merely disagreed with the arbitrator’s construction of it.
The collective bargaining agreement could have provided that if any of the employees were wrongfully discharged, the remedy would be reinstatement and back pay up to the date they were returned to work. Respondent’s major argument seems to be that by applying correct principles of law to the interpretation of the collective bargaining agreement it can be determined that the agreement did not so provide, and that therefore the arbitrator’s decision was not based upon the contract. The acceptance of this view would require courts, even under the standard arbitration clause, to review the merits of every construction of the contract. This plenary review by a court of the merits would make meaningless the provisions that the arbitrator’s decision is final, for in reality it would almost never be final. This underlines the fundamental error which we have alluded to in United Steelworkers of America v. American Manufacturing Co., ante, p. 564, decided this day. As we there emphasized, the question of interpretation of the collective bargaining agreement is a question for the arbitrator. It is the arbitrator’s construction which was bargained for; and so far as the arbitrator’s decision concerns construction of the contract, the courts have no business overruling him because their interpretation of the contract is different from his.
We agree with the Court of Appeals that the judgment of the District Court should be modified so that the amounts due the employees may be definitely determined by arbitration. In all other respects we think the judgment of the District Court should be affirmed. Accordingly, we reverse the judgment of the Court of Appeals, except for that modification, and remand the case to the District Court for proceedings in conformity with this opinion.
It is so ordered.
Mr. Justice Frankfurter concurs in the result.
Mr. Justice Black took no part in the consideration or decision of this case.
[For opinion of Mr. Justice Brennan, joined by Mr. Justice Frankfurter and Mr. Justice Harlan, see ante, p. 569.]
See Textile Workers v. Cone Mills Corp., 268 F. 2d 920 (C. A. 4th Cir.).
“Persons unfamiliar with mills and factories — farmers or professors, for example — often remark upon visiting them that they seem like another world. This is particularly true if, as in the steel industry, both tradition and technology have strongly and uniquely molded the ways men think and act when at work. The newly hired employee, the ‘green hand,’ is gradually initiated into what amounts to a miniature society. There he finds himself in a strange environment that assaults his senses with unusual sounds and smells and often with different ‘weather conditions’ such as sudden drafts of heat, cold, or humidity. He discovers that the society of which he only gradually becomes a part has of course a formal government of its own — the rules which management and the union have laid down — but that it also differs from or parallels the world outside in social classes, folklore, ritual, and traditions.
“Under the process in the old mills a very real ‘miniature society’ had grown up, and in important ways the technological revolution described in this case history shattered it. But a new society or work community was born immediately, though for a long time it developed slowly. As the old society was strongly molded by the discontinuous process of making pipe, so was the new one molded by the continuous process and strongly influenced by the characteristics of new high-speed automatic equipment.” Walker, Life in the Automatic Factory, 36 Harv. Bus. Rev. Ill, 117.
See Jalet, Judicial Review of Arbitration: The Judicial Attitude, 45 Cornell L. Q. 519, 522.

Question: What is the basis of the Supreme Court's decision?

Choices:
judicial review (national level)
judicial review (state level)
Supreme Court supervision of lower federal or state courts or original jurisdiction
statutory construction
interpretation of administrative regulation or rule, or executive order
diversity jurisdiction
federal common law

Answer: 2