with whom Justice Brennan, Justice Marshall, and Justice BLACKMUNjoin, concurring in the judgment.
Congress has authorized interested parties to petition the Interstate Commerce Commission (ICC or Commission) to reopen a proceeding, grant rehearing or reconsideration, or change an action of the Commission “because of material error, new evidence, or substantially changed circumstances.” 49 U. S. C. § 10327(g). The statute draws no distinction between petitions alleging that the action was based on “material error” and petitions alleging “new evidence, or substantially changed circumstances.” Nor does the Hobbs Act, 28 U. S. C. § 2341 et seq., which affords judicial review of agency orders, recognize any such distinction. Yet, solely because it believes that such a distinction is desirable as a matter of policy, the Court today fashions a new rule of “jurisdiction.”
The Court holds that agency decisions denying petitions for reopening based on “material error” are not subject to judicial review, even if the denial is arbitrary or contrary to law. Because this holding is not supported by the relevant statutes, and is contrary to longstanding principles of administrative law, I cannot subscribe to it. Addressing the merits, I conclude that the Court of Appeals erred in reversing the ICC’s decisions not to reopen the matter before it. To the extent that the Commission based those decisions on its reading of the statute, its reading was correct; to the extent that it refused to consider issues not raised previously, it did not abuse its discretion.
I
The Administrative Orders Review Act, 28 U. S. C. § 2341 et seq., commonly known as the Hobbs Act, is quite plain in *288spelling out when and where parties may file petitions for judicial review of agency decisions. After stating that the courts of appeals have exclusive jurisdiction to “enjoin, set aside, suspend (in whole or in part), or to determine the validity of all rules, regulations, or final orders of the Interstate Commerce Commission,” 28 U. S. C. § 2342 (except for certain orders not relevant here which are reviewed in the district courts, see 28 U. S. C. § 2321), the Act provides:
“Any party aggrieved by the final order may, within 60 days after its entry, file a petition to review the order in the court of appeals where venue lies.” 28 U. S. C. §2344.
The Court appears to agree that all of these elements were satisfied here. The denials of reopening and reconsideration constituted final orders; respondents were aggrieved parties; the petitions were filed within the required time period; and venue was appropriate in the United States Court of Appeals for the District of Columbia Circuit. Nonetheless, the Court concludes that the Court of Appeals should have dismissed the petitions for want of jurisdiction.
I agree with the Court that the only agency actions properly before the Court of Appeals were the ICC’s denial of clarification served on May 18, 1983 (which the Court properly treats as a motion to reopen), and the ICC’s denial of reconsideration served on October 25, 1983. I also agree that, depending on an agency’s regulations, a decision whether to reopen may be based on discretionary factors that will virtually always survive judicial review. But this does not divest the courts of appeals of jurisdiction; it simply means that an agency’s decision based on such discretionary considerations will almost always, if not always, be upheld as not “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” 5 U. S. C. §706(2)(A). See United States v. Pierce Auto Freight Lines, Inc., 327 U. S. 515, 535 (1946).
Not every denial of a petition for reopening is premised on discretionary considerations. In many contexts the agency’s *289authority to exercise its discretion is limited by regulation, and the agency may choose to justify its denial of the petition on the ground that those criteria have not been satisfied. Here, for example, the regulations allowed the Commission to grant a petition for reopening of a decision reached by the entire Commission only if the petitioner could show either that “[t]he prior action . . . will be affected materially because of new evidence or changed circumstances,” or that the prior action “involves material error.” 49 CFR §1115.3 (1986). Similarly, a statute provides that the Commission may only supplement a prior order approving consolidations and related transactions if “cause exists,” 49 U. S. C. § 11351, a term that has been interpreted narrowly by some courts. See Illinois v. ICC, 713 F. 2d 305, 310 (CA7 1983); Greyhound Corp. v. ICC, 215 U. S. App. D. C. 322, 330, 668 F. 2d 1354, 1362 (1981). When an agency denies rehearing on a legal ground, such as when it premises its decision on its reading of the statute, the reviewing court has a significant role to play; it must decide whether that reading can be sustained, or whether it is contrary to law.1 As we explained in Pierce Auto Freight Lines, the court’s job is to ascertain *290“whether there is warrant in the.law and the facts for what the Commission has done.” 327 U. S., at 536.
One of the basic tenets of judicial review of agency decisions is that “an agency’s order must be upheld, if at all, ‘on the same basis articulated in the order by the agency itself.’” FPC v. Texaco, Inc., 417 U. S. 380, 397 (1974), quoting Burlington Truck Lines, Inc. v. United States, 371 U. S. 156, 168-169 (1962). As the Court explained in SEC v. Chenery Corp., 332 U. S. 194 (1947):
“[A] simple but fundamental rule of administrative law . . . is . . . that a reviewing court, in dealing with a determination or judgment which an administrative agency alone is authorized to make, must judge the propriety of such action solely by the grounds invoked by the agency. If those grounds are inadequate or improper, the court is powerless to affirm the administrative action.” Id., at 196.2
Consequently, when an agency explains that it has denied a petition for reopening based on its understanding of the underlying statute, a reviewing court may only uphold the agency decision if that reasoning withstands review. To be sure, an agency may announce that it has declined to consider the petition for reopening because it is duplicative, because it was filed so late in the day, or for some other discretionary consideration. If the agency explains its decision on such grounds, its reasoning must be scrutinized under an abuse-of-discretion standard.3 But if the agency chooses not to pro*291ceed in that fashion and to base its decision on its reading of a statute or a constitutional provision, its decision cannot be sustained on the conjecture that it has the discretion to deny reopening on a variety of grounds. If the court of appeals finds legal error, it must remand the case to the agency, which may then consider whether to exercise its discretion to grant the petition for reopening.4 This is the lesson of Chenery and its progeny — a lesson the Court ignores today when it claims that “it is the Commission’s formal action, rather than its discussion, that is dispositive.” Ante, at 281.
The Court argues that it would be more prudent to require the parties to seek review in the court of appeals immediately after an agency’s initial decision. This may or may not be true.5 But our view of efficient procedure does not give us the power to rewrite the United States Code or the Code of Federal Regulations. Nor does it justify ignoring this Court’s decisions explicitly holding that a denial of a petition for reopening is reviewable, see Giova v. Rosenberg, 379 U. S. 18 (1964); reversing an agency for failing to reopen a *292matter, see Atchison, T. & S. F. R. Co. v. United States, 284 U. S. 248 (1932);6 or reviewing denials of petitions for reopening, see, e. g., Radio Corporation of America v. United States, 341 U. S. 412, 420-421 (1951); Acker v. United States, 298 U. S. 426, 432-433 (1936); St. Joseph Stock Yards Co. v. United States, 298 U. S. 38, 47-49 (1936); United States v. Northern Pacific R. Co., 288 U. S. 490, 492-494 (1933); see also INS v. Rios-Pineda, 471 U. S. 444 (1985); INS v. Jong Ha Wang, 450 U. S. 139 (1981). In many of these cases we have stressed the limited role courts play in reviewing agency denials of reopening; but, until today, we have never held that the courts lack jurisdiction to review the decisions at all.7 As Judge Friendly put it:
*293“The fact that reopening is a matter of agency discretion to a considerable extent. . . does not lead inevitably to a conclusion that such an exercise of administrative power is wholly immune from judicial examination; § 10 (e) of the APA expressly authorizes the courts to set aside any administrative decision constituting an abuse of discretion. The question is whether the Secretary in deciding not to reopen enjoys absolute discretion .... Absent any evidence to the contrary, Congress may rather be presumed to have intended that the courts should fulfill their traditional role of defining and maintaining the proper bounds of administrative discretion.” Cappadora v. Celebrezze, 356 F. 2d 1, 5-6 (CA2 1966).8
The Court brushes off the many cases reviewing denials of petition for reopening by distinguishing between petitions for reopening based upon new evidence or changed circumstances and those based upon claims of material error. *294Ante, at 278-280. According to the Court, denials of petitions for reopening that involve allegations of “new evidence” or “changed circumstances” are reviewable. Similarly, decisions reached after reopening are reviewable, even if the agency merely reaffirms its earlier decision. But, the Court proclaims, denials of petitions to reopen that allege only material error are not reviewable. Whether or not such a distinction might be reasonable, it is nevertheless a pure creature of judicial invention. I am unable to join such a creative reading of the plain language of the Hobbs Act.9
The Court’s reliance on 5 U. S. C. § 701(a)(2) for the proposition that denials of petitions for reopening are nonreviewable because they are “committed to agency discretion by law” is conclusively rebutted by the Court’s own analysis. If denials of petitions to reopen based on material error are discretionary then so are denials of petitions to reopen based on new facts or changed circumstances. Yet the Court concedes, as it must, that denials of petitions claiming new facts or changed circumstances are reviewable, notwithstanding the discretionary element. Heckler v. Chaney, 470 U. S. 821 (1985), does not speak to this issue. Unlike a prosecutor’s or an agency’s decision not to take enforcement action, there is no dearth of “judicially manageable standards” in this context. Nor is there any basis for the Court’s ability to “perceive that a . . . tradition of nonreviewability exists with regard to refusals to reconsider for material error.” Ante, at 282. I am not sure what the Court’s source for this tradition is, but it is surely not to be found in the decisions of the courts or in anything that Congress has said.
It seems clear to me that neither the Hobbs Act nor the Administrative Procedure Act recognizes the distinction that *295the Court creates today. Thus, I am compelled to conclude, as the ICC itself recognizes, see Supplemental Memorandum for ICC 4, that the petitions for review in this case were timely, but only for the purpose of reviewing the Commission’s orders denying clarification and reconsideration.
I — I I — I
The Commission s decisions denying the petitions for clarification and reconsideration in this case were based partly on discretionary considerations and partly on the Commission’s interpretation of the relevant law. The Commission read the statute as not requiring it to make a “necessity” finding (which it had not made), and concluded that any deficiencies in the “public interest” findings that it was required to make (and had made) were attributable to the unions’ failure to raise the issue in the initial proceeding. I believe that the Commission’s legal conclusion was sound, and that it did not abuse its discretion in refusing to consider facts and theories that the unions could have brought up in their original objections to the transactions.
The petitions for clarification and reconsideration apparently were prompted by the unions’ belated realization that the Missouri-Kansas-Texas Railroad Co. (MKT) and the Denver and Rio Grande Western Railroad Co. (DRGW) believed that they had the right to use their own crews to operate trains pursuant to their newly granted trackage rights over the Union Pacific Railroad Company’s (UP) and Missouri Pacific Railroad Company’s (MP) tracks. The unions argued that the Railway Labor Act (RLA), certain provisions of the Interstate Commerce Act (ICA), and their collective-bargaining agreements, gave UP and MP employees certain rights with respect to working those tracks. The MKT and DRGW, on the other hand, argued that even if such rights existed, the ICC had approved MKT’s and DRGW’s applications for trackage rights, and the applications had specified that the two railroads had the right to utilize their own *296crews. In light of the ICC’s approval, the railroads concluded, they were exempt under 49 U. S. C. § 11341 from any conflicting law on the question of who would crew the trains. That statute provides:
“A carrier, corporation, or person participating in [an] approved or exempted transaction is exempt from the antitrust laws and from all other law, including State and municipal law, as necessary to let that person carry out the transaction, hold, maintain, and operate property, and exercise control or franchises acquired through the transaction.”
In its denials of the petitions for clarification and reconsideration, the ICC rejected the unions’ argument that in order for the exemption provision of § 11341 to come into play, the ICC must make an actual, on the record, determination that the exemption is “necessary” to the transaction. The Commission explained:
“The terms of Section 11341 immunizing an approved transaction from any other laws are self-executing and there is no need for us expressly to order or to declare that a carrier is specifically relieved from certain restraints. See Brotherhood of Loc. Eng. [v. Chicago & N. W. R. Co., 314 F. 2d 424, 430-431 (CA8), cert denied, 375 U. S. 819 (1963)], citing Chicago, St. P., M. & O. Ry. Lease, 295 I. C. C. 696, at 432 (1958).
“In evaluating a transaction under the criteria of 49 U. S. C. 11344, we must consider the policies of statutes other than the Interstate Commerce Act to the extent that those policies are relevant to the determination of whether a proposal is consistent with the public interest. For example, the public interest evaluation must include consideration of the policies of the antitrust laws. See McLean Trucking Co. v. United States, 321 U. S. 67, 87 (1944).
*297“While the RLA, like the antitrust laws, embodies certain public policy considerations, the Interstate Commerce Act also specifies that interests of affected employees must be considered. In these proceedings, we gave full consideration to the impact of the consolidation on railroad employees in accordance with our established policies. 366 I. C. C. 618-22.
“The record in these proceedings is devoid of any suggestion by BLE, UTU, or any other party that the approval of the responsive trackage rights applications, subject to the usual labor protective conditions, would be in any way inconsistent with the policies of the RLA. In these circumstances, we can find no merit in UTU’s argument that we improperly failed to reconcile the policies of the RLA with our decision.” App. to Pet. for Cert. in No. 85-793, pp. A44-A45.
The Court of Appeals reversed, rejecting the ICC’s argument that § 11341 is self-executing and that the Commission need not make any explicit necessity findings. 245 U. S. App. D. C. 311, 320, 761 F. 2d 714, 723 (1985). The court explained that “Congress has given ICC broad powers to immunize transactions from later legal obstacles, but this delegation by Congress is explicitly qualified by a necessity component. ... In exercising its waiver authority ICC must do more than shake a wand to make a law go away. It must supply a reasoned basis for that exercise of its statutory authority.” Ibid. Because it did not believe that the ICC had supplied justification for the necessity of waiving any RLA provisions regarding crew selection, the Court remanded the case for the ICC to determine whether it should “exercise its exemption authority.” Id., at 322, 761 F. 2d, at 725. Judge MacKinnon dissented, arguing that the statute is self-executing, and that the ICC is not required to make *298any finding of necessity. Id., at 326-332, 761 F. 2d, at 729-736.10
The Court of Appeals’ holding was based on a misunderstanding of § 11341. That statute, as its plain language indicates, does not condition exemptions on the ICC’s announcing that a particular exemption is necessary to an approved transaction. Rather, § 11341 automatically exempts a person from “other laws” whenever an exemption is “necessary to let that person carry out the transaction, hold, maintain, and operate property, and exercise control or franchises acquired through the transaction.” The breadth of the exemption is defined by the scope of the approved transaction,11 and no explicit announcement of exemption is required to make the statute applicable. As this Court explained with reference to § 11341’s predecessor:
“[A]pproval of a voluntary railroad merger which is within the scope of the Act is dependent upon three, and upon only three, considerations: First, a finding that it ‘will be consistent with the public interest.’ (§ 5 (2)(b).) Second, a finding that, subject to any modification made by the Commission, it is ‘just and reasonable.’ (§5 (2) (b).) Third, assent of a ‘majority ... of the holders of the shares entitled to vote.’ (§6(11).) When these *299conditions have been complied with, the Commission-approved transaction goes into effect without the need for invoking any approval under state authority, and the parties are relieved of ‘restraints, limitations, and prohibitions of law, Federal, State, or municipal, insofar as may be necessary to enable them to carry into effect the transaction so approved...(§5 (11).)-” Schwabacher v. United States, 334 U. S. 182, 194 (1948).
See also Seaboard Air Line R. Co. v. Daniel, 333 U. S. 118, 124 (1948) (not necessary for Commission’s order to manifest “a clear purpose to authorize the exemption”); 49 U. S. C. § 11344(b) (listing items that Commission must consider in evaluating mergers). The present statute is no different in this respect; the exemption is self-executing.12
*300Of course, as the Commission explained, in conducting the public interest inquiry under 49 U. S. C. §11344 the Commission must consider that the legal consequence of approving the transaction as proposed will be to exempt the parties from the dictates of “other laws” to the extent necessary to carry out the transaction.13 See McLean Trucking Co. v. United States, 321 U. S. 67, 79-88 (1944). But this is a far cry from requiring the Commission to predict exactly what type of exemptions will be required and, for each one, whether the transaction could survive absent the exemption.14
*301In its decision on the petition for reconsideration the Commission stated that it had considered the effect of the transaction on rail labor in its public interest calculations. Indeed, the original decision approving the transactions included a four-page discussion about its effect on labor, see Union Pacific—Control—Missouri Pacific, Western Pacific, 366 I. C. C. 462, 618-622 (1982)—issues the Commission is explicitly required to consider pursuant to 49 U. S. C. § 11344(b), and 49 U. S. C. §11347 (1982 ed., Supp. III). Generally, the Commission concluded that the “transactions will directly benefit labor both by producing a substantial net increase in existing and future employment opportunities and by increasing the job security of their present employees.” 366 I. C. C., at 619. To be sure, as the Commission itself recognized in its denial of the motion for reconsideration, it never explicitly considered the public interest ramifications of displacing any RLA provisions involving whose crew should be used in the newly granted trackage rights. But the ICC explained that it had not considered that issue because none of the unions had ever suggested that anything proposed by the railroads, including the MKT’s and DRGW’s use of their own crews, would be inconsistent with the RLA.
It is on this last point that the special considerations involving review of an agency’s refusal to reopen a matter come into play. The agency clearly has the right to deny reopening to a party who failed to present evidence or to raise an objection that could have been presented or raised before the agency’s initial decision was reached.15 Indeed, even at the *302time of the petition for clarification, the Commission did not believe that the unions had adequately supported their contention that the RLA had anything to say about the trackage rights issue.16 Similarly, the Commission declined to address the other issues that the unions raised, such as whether MKT’s and DRGW’s use of their own crews violated the terms of the labor protective conditions that the Commission had imposed in the approval order. See App. to Pet. for Cert. in No. 85-793, pp. A45-A50 (discussing the terms imposed pursuant to New York Dock R. Co.—Control—Brooklyn Eastern Dist., 360 I. C. C. 60 (1979), and Norfolk & Western R. Co.—Trackage Rights—BN, 354 I. C. C. 605 (1978), as modified by Mendocino Coast R. Co.—Lease and Operate, 360 I. C. C. 653, 664 (1980)). Surveying the many opportunities that the unions had to raise objections to the trackage rights proposals during the proceedings, the Commission concluded:
“BLE, UTU, and various other railway labor organizations participated in these proceedings, and none made any argument or presented any evidence that the responsive trackage rights proposals would violate any applicable labor agreement. Rather, the record supports the conclusion that the trackage rights operations, using the tenants’ crews, could be implemented as approved without raising any dispute over crew assignments between the employees of different railroads.” App. to Pet for Cert. in No. 85-793, p. A45.
It is thus clear that the agency’s refusal to take action based on the unions’ new claim that the use of the tenants’ crews conflicted with various laws was based on the premise that *303the unions had, so to speak, procedurally defaulted on those claims. There is no basis for concluding that this decision constituted an abuse of discretion.
I would therefore reverse the Court of Appeals on these grounds, not because it lacked jurisdiction.
In Heckler v. Chaney, 470 U. S. 821 (1985), the Court held that agency decisions not to take enforcement action are generally committed to agency discretion by law under 5 U. S. C. § 701(a)(2). Even so, the Court stressed that it was not dealing with “a refusal by the agency to institute proceedings based solely on the belief that it lacked jurisdiction.” Id., at 833, n. 4; see also NAACP v. FPC, 425 U. S. 662 (1976) (reviewing agency’s refusal to promulgate rule because refusal was based on agency’s contention that it lacked jurisdiction); International Union, United Automobile, Aerospace, & Agricultural Implement Workers v. Brock, 251 U. S. App. D. C. 239, 247, 783 F. 2d 237, 245 (1986) (distinguishing decisions announcing that agency will not take enforcement action from decisions announcing substantive statutory interpretations).
Of course, an agency may, if it chooses, deny the petition on discretionary grounds -without considering whether the petition makes a showing sufficient to support reopening under the statute or regulations. See INS v. Bagamasbad, 429 U. S. 24, 26 (1976).
Contrary to the Court’s suggestion, ante, at 282-288, I do not believe that Chenery establishes whether agency action is reviewable. Chenery does, however, powerfully rebut the Court’s contention that there is nothing to review when an agency bases a decision on an erroneous legal ground when it could have denied relief on discretionary grounds.
The Court ignores this fact when it claims that litigants will routinely disregard the Hobbs Act’s 60-day limit on judicial review unless denials of reopening are declared nonreviewable. Because an agency has the right to reject the petition on discretionary grounds, without reaching the mate*291rial error alleged by the party, see n. 1, supra, litigants have the strongest of incentives to seek timely review of the agency’s original decision.
That many or even most denials of petitions for reopening are made without statements of reasons does not make judicial review unworkable. Of course, to the extent that 5 U. S. C. § 555(e) allows the agency to announce its denial without a statement, it may continue to do so. See Vermont Yankee Nuclear Power Corp. v. Natural Resources Defense Council, Inc., 435 U. S. 519 (1978). In such a case, the reviewing court may properly presume that the decision was reached on ordinary discretionary considerations, and may review the decision on that basis to ascertain whether it constitutes an abuse of discretion.
In some cases, an agency might base its order denying reopening on a new legal ground which it had not included in its original decision. Alternatively, the agency may clarify its earlier decision in a manner that gives rise to new legal challenges. In either event, it is surely unfair to deprive the aggrieved party of judicial review of an agency interpretation which he or she had no prior opportunity to challenge. The Court seems to agree that such an order would be reviewable, see ante, at 286, but, of course, cannot square this position with its newfound rule of “jurisdiction.”
The Court is correct in observing that Atchison, T. & S. F. R. Co. “was ‘promptly restricted ... to its special facts, . . . and . . . stands virtually alone.”’ Ante, at 278, quoting ICC v. Jersey City, 322 U. S. 503, 515 (1944). But the unique aspect of the case is that it reversed the agency action — not that it reviewed the agency action.
In Califano v. Sanders, 430 U. S. 99 (1977), the Court held that judicial review was unavailable from the Secretary of Health, Education, and Welfare’s final decision not to reopen a claim for benefits. The Court rested this holding on the statutory language there, which provides that an individual may seek review by commencing a civil action within 60 days “after any final decision of the Secretary made after a hearing.” 42 U. S. C. § 405(g). The Court explained that “[t]his provision clearly limits judicial review to a particular type of agency action, a ‘final decision of the Secretary made after a hearing.’” 430 U. S., at 108. A denial of a petition for reopening did not satisfy this language, and the Court felt compelled “to respect” Congress’ choice. Ibid. Similarly, in SEC v. Louisiana Public Service Comm’n, 353 U. S. 368 (1957), the Court held that the specific judicial review language in 15 U. S. C. § 79k(b), which dealt with Commission orders that “revoke or modify” a previous order, restricted judicial review to the orders listed in the statute. Neither Sanders nor Louisiana Public Service Comm’n is relevant here for no such restrictive language applies to review of ICC decisions under the Hobbs Act.
The Court’s citation of Court of Appeals decisions supporting its non-review position, ante, at 280, is not at all conclusive. Many decisions have held that such petitions are indeed reviewable. See Carter/Mondale Presidential Committee, Inc. v. FEC, 249 U. S. App. D. C. 349, 353-354, 775 *293F. 2d 1182, 1186-1187 (1985); Wausau v. United States, 703 F. 2d 1042 (CA7 1983); Virginia Appalachian Lumber Corp. v. ICC, 197 U. S. App. D. C. 13, 19, 606 F. 2d 1385, 1391 (1979); Provisioners Frozen Express, Inc. v. ICC, 536 F. 2d 1303, 1305 (CA9 1976); B. F. Goodrich Co. v. Northwest Industries, Inc., 424 F. 2d 1349, 1355 (CA3), cert. denied, 400 U. S. 822 (1970); Northeast Broadcasting, Inc. v. FCC, 130 U. S. App. D. C. 278, 287-288, 400 F. 2d 749, 758-759 (1968). Cases reviewing denials of reopening in the immigration context are too common to require citation.
In Provisioners Frozen Express, supra, the court dealt with a petition for review which, like the one here, had been filed more than 60 days after the initial decision, but within 60 days of the petition for reopening. The court held that the Commission’s refusal to entertain the petition for reopening “did not create a new final order which would give the Court jurisdiction to review some five years of proceedings in this matter.” Id., at 1305. But, the court hastened to add, it did have jurisdiction to determine “whether the Commission abused its discretion in rejecting [the] petition to reopen.” Ibid.
Although, given the intervening decision in Sanders, supra, this case is no longer good law with respect to review of Social Security determinations, Judge Friendly’s discussion on the general issue of denials of petitions to reopen continues to merit our respect.
The only statute other than the Hobbs Act that the Court refers to on this matter is 49 U. S. C. § 10327(i) which specifies when an ICC order becomes final. That provision does not speak to the question of what types of orders are reviewable, and I do not read the Court’s opinion as relying on it.
Judge MacKinnon also dissented from the Court of Appeals’ holding that the petition was filed within sufficient time as to call into question the ICC’s initial decision. 245 U. S. App. D. C., at 322-326, 761 F. 2d, at 725-729.
There may, of course, be some limitations on the types of matters the ICC can approve as part of a transaction. See Palestine v. United States, 559 F. 2d 408, 414 (CA5 1977), cert. denied, 435 U. S. 950 (1978) (looking at whether ICC approval was “germane to the success of the . . . transaction”). The Commission stated in this case that “[pjrovisions of trackage rights agreements designating which carrier’s employees will perform trackage rights operations are material terms of the agreement.” App. to Pet. for Cert. in No. 85-793, p. A50. In his dissent, Judge Mac-Kinnon elaborated on this point. 245 U. S. App. D. C., at 329, 761 F. 2d, at 732.
The legislative history of § 11341 supports the meaning derived from its plain language. Section 407 of the Transportation Act of 1920, ch. 91, 41 Stat. 480, authorized Commission approvals of consolidations, and included a section providing:
“The carriers affected by any order made under the foregoing provisions of this section . . . shall be, and they are hereby, relieved from the operation of the ‘antitrust laws,’. . . and of all other restraints or prohibitions by law, State, or Federal, in so far as may be necessary to enable them to do anything authorized or required by an order made under and pursuant to the foregoing provisions of this section.” 41 Stat. 482, amending § 5(8) of the Interstate Commerce Act.
The operative language, with its self-executing phraseology, was incorporated into the 1940 amendment and recodification of the Transportation Act. See § 7 of the Transportation Act of 1940, ch. 722, 54 Stat. 908-909, amending §5 (11). Again, when the Act was recodified as 49 U. S. C. § 11341(a), no substantive change was affected. Pub. L. 95-473, § 3(a), 92 Stat. 1466. See H. R. Rep. No. 95-1395, pp. 158-168 (1978).
In addition, the Commission has consistently treated the exemption as automatically flowing from an approval. See, e. g., Railway Express Agency, Inc., Notes, 348 I. C. C. 157, 215 (1975); Ex Parte No. 260, Revised Regulations Governing Interlocking Officers, 336 I. C. C. 679, 681-682 (1970); Texas Turnpike Authority Abandonment by St. Louis Southwestern R. Co., 328 I. C. C. 42, 46 (1965); Chicago, St. P., M. & O. R. Co. Lease, 295 I. C. C. 696, 702 (1958); Control of Central Pacific by Southern Pacific, 76 I. C. C. 508, 515-517 (1923). A number of Courts of *300Appeals have agreed. See Missouri Pacific R. Co. v. United Transportation Union, 782 F. 2d 107, 111 (CA8 1986), cert. pending, No. 85-1054; Brotherhood of Locomotive Engineers v. Chicago & N. W. R. Co., 314 F. 2d 424 (CA8), cert. denied, 375 U. S. 819 (1963).
This does not mean, as respondents fear, that a party claiming an exemption on the basis of § 11341 need merely assert that its conduct is “necessary” in order to prevail in its claim. Any tribunal that is faced with a claim that a party is violating some “other law” has the responsibility of determining whether an exemption is “necessary to let that person carry out the transaction, hold, maintain, and operate property, and exercise control or franchises acquired through the transaction.” 49 U. S. C. § 11341. See Railway Express Agency, supra, at 215-218.
The Court of Appeals appeared to recognize the problems of its suggested approach when it agreed that the ICC need not “enumerate every legal obstacle that is waived in its approval,” since to require the Commission to contemplate unforeseeable legal obstacles to fruition of the transaction would “undermine the approval authority’s purpose of ‘facilitating] merger and consolidation in the national transportation system.’” 245 U. S. App. D. C. 311, 320, n. 4, 761 F. 2d 714, 723, n. 4 (1985), quoting County of Marin v. United States, 356 U. S. 412, 416 (1958). But, the court nonetheless held that the “ICC’s decisionmaking process, either in the approval or in a later proceeding, must reveal evidence supporting a conclusion that waiver of a particular legal obstacle is necessary to effectuate the transaction.” 245 U. S. App. D. C., at 320, n. 4, 761 F. 2d, at 723, n. 4. The idea of having parties repeatedly return to the ICC for decisions on the necessity of an exemption is without basis in the statutory scheme, and would clearly not mitigate the delay and confusion surrounding consolidations.
1 find no merit in respondents’ suggestion that they had no notice that the Commission might consider allowing the MKT and DRGW to use their own crews in connection with their newly acquired trackage rights. Although the Commission’s approval may have been ambiguous on this issue (the Commission does not think it was), the trackage rights proposals submitted by the MKT and DRGW explicitly stated that the railroads wished to be allowed to use their own crews. See ante, at 273-274; see also Missouri Pacific R. Co., supra, at 112; App. to Pet. for Cert. in No. 85-793, pp. A45-A50. The ICC’s conclusion that the unions should have been *302aware of the terms of the proposals is entitled to substantial deference, resting as it does on the intricacies of practice before the Commission.
The Commission prefaced its discussion of the §11341 issue by concluding that the unions had not adequately demonstrated that “the track-age rights agreements . . . involve a change in UP-MP employees’ working conditions in a manner contrary to RLA requirements.” Id,., at A43.