[1464]*1464Opinion for the Court filed by Circuit Judge WILLIAMS.
Concurring opinion filed by Circuit Judge SENTELLE.
Dissenting opinion filed by Chief Judge MIKVA.
STEPHEN F. WILLIAMS, Circuit Judge:
Sweet Home Chapter of Communities for a Great Oregon and a number of other organizations (collectively referred to here as “Sweet Home”) sued in district court to invalidate a number of regulations promulgated by the Fish & Wildlife Service of the Interior Department under the Endangered Species Act of 1973 (“ESA” or the “Act”), 16 U.S.C. §§ 1531^4 (1988). The district court rejected all the challenges, 806 F.Supp. 279, and this court affirmed, unanimously except as to one issue. Sweet Home Chapter v. Babbitt, 1 F.3d 1 (D.C.Cir.1993). The issue that split the court involved the scope of the Act’s prohibition of the “taking” of endangered species. On petition for rehearing, and after securing a response from the government, we alter our view on that issue.
The Act makes it a crime for any person to “take” any endangered species of fish or wildlife listed under the Act. ESA § 9(a)(1)(B), 16 U.S.C. § 1538(a)(1)(B). A definitional section of the Act states that “take” means
to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.
16 U.S.C. § 1532(19). The Fish & Wildlife Service (“FWS”) has in turn defined the component term “harm” in such a way as to encompass any “significant” habitat modification that leads to an injury to an endangered species of wildlife:
Harm in the definition of “take” in the Act means an act which actually kills or injures wildlife. Such act may include significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding or sheltering.
50 CFR § 17.3.
The government contends that the Act as originally adopted in 1973 authorized this expansive definition, and that even if it did not, a 1982 amendment to another provision of the ESA, specifically § 10(a)(1)(B) of the Act, 16 U.S.C. § 1539(a)(1)(B), either so changed the context of the “take” definition as to validate the Service’s definition, or at any rate ratified that definition.
On petition for rehearing, we reject both theories. We find that the Service’s definition of “harm” was neither clearly authorized by Congress nor a “reasonable interpretation” of the statute, see Chevron U.S.A. Inc. v. Natural Resources Defense Council, 467 U.S. 837, 842-43, 844, 104 S.Ct. 2778, 2781-82, 2782, 81 L.Ed.2d 694 (1984), and we find that no later action of Congress supplied the missing authority.
The language, structure and legislative history of the 1978 Act
The Fish & Wildlife Service found habitat modification within the idea of “harm”, the most elastic of the words Congress used to define the acts that § 9 of the ESA forbids private individuals to commit. The potential breadth of the word “harm” is indisputable. In Lucas v. South Carolina Coastal Council, — U.S. -, 112 S.Ct. 2886, 120 L.Ed.2d 798 (1992), for example, the Supreme Court, in exploring the just compensation requirement of the 5th Amendment, observed that “the distinction between ‘harm-preventing1 and ‘benefit-conferring’ regulations is often in the eye of the beholder.” Id. — U.S. at -, 112 S.Ct. at 2897. As a matter of pure linguistic possibility one can easily recast any withholding of a benefit as an infliction of harm. In one sense of the word, we “harm” the people of Somalia to the extent that we refrain from providing humanitarian aid, and we harm the people of Bosnia to the extent that we fail to stop “ethnic cleansing”. By the same token, it is linguistically possible to read “harm” as referring to a landowner’s withholding of the benefits of a habitat that is beneficial to a species. A farmer who harvests crops or [1465]*1465trees on which a species may depend harms it in the sense of withdrawing a benefit; if the benefit withdrawn be important, then the Service’s regulation sweeps up the farmer’s decision.
The immediate context of the word, however, argues strongly against any such broad reading. With the single exception of the word “harm”, the words of the definition contemplate the perpetrator’s direct application of force against the animal taken: “harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect”. The forbidden acts fit, in ordinary language, the basic model “A hit B.”
For some of the words, to be sure, the application of force may not be instantaneous or immediate, and the force may not involve a bullet or blade. In the case of “pursue”, the perpetrator does not necessarily catch or destroy the animal, but pursuit would always or almost always be a step toward deliberate capture or destruction, and so would be picked up by § 1532(19)’s reference to “attempt[s]”. While one may “trap” an animal without being physically present, the perpetrator will have previously arranged for release of the energy that directly captures the animal. And one may under some circumstances “harass” an animal by aiming sound or light in its direction, but the waves and particles are themselves physical forces launched by the perpetrator. Interpreting “harass” in the Marine Mammal Protection Act, where it appears as one of the components of “take” (defined as “to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal”), the 9th Circuit applied noscitur a sociis, saying:
The statute groups “harass” with “hunt,” “capture,” and “kill” as forms of prohibited “taking.” The latter three each involve direct, sustained, and significant intrusions upon the normal, life-sustaining activities of a marine mammal; killing is a direct and permanent intrusion, while hunting and capturing cause significant disruptions of a marine mammal’s natural state. Consistent with these other terms, “harassment,” to constitute a “taking” under the MMPA, must entail a similar level of direct and sustained intrusion.
United States v. Hayashi, 5 F.3d 1278, 1282 (9th Cir.1993). Accordingly the court overturned the defendant’s conviction. Although he had fired a rifle twice into the water behind some porpoises, he had not harassed the porpoises within the meaning of the statute, as his acts were not “direct and significant intrusions upon the mammal’s ordinary activities.” Id. Here, the nine verbs accompanying “harm” all involve a substantially direct application of force, which the Service’s concept of forbidden habitat modification altogether lacks.1
The implications of the Service’s definition suggest its improbable relation to congressional intent. Species dependency may be very broad. One adherent of aggressive protection, for instance, notes that “[s]ome scientists believe as many as 35 million to 42 million acres of land are necessary to the survival of grizzlies”, about as much land in the northern Rockies of the United States and Canada as is still usable grizzly habitat. Rocky Barker, Saving All the Parts 34 (1993). And for an individual to “knowingly” violate § 9 means criminal penalties of up to a $100,000 fine and imprisonment for one year. See 16 U.S.C. § 1540(b); 18 U.S.C. §§ 3559(a)(6), 3571(b) and (e) (raising the maximum penalty).
Thus the gulf between the Service’s habitat modification concept of “harm” and the other words of the statutory definition, and the implications in terms of the resulting extinction of private rights, counsel application of the maxim noscitur a sociis. “The maxim noscitur a sociis, that a word is known by the company it keeps, while not an inescapable rule, is often wisely applied where a word is capable of many meanings in order to avoid the giving of unintended breadth to the Acts of Congress.” Jarecki v. G.D. Searle & Co., 367 U.S. 303, 307, 81 S.Ct. 1579, 1582, 6 L.Ed.2d 859 (1961). See also [1466]*1466Dole v. Steelworkers, 494 U.S. 26, 36, 110 S.Ct. 929, 935, 108 L.Ed.2d 23 (1990) (“words grouped in a list should be given related meaning”) (citations omitted).2 The Service’s interpretation appears to yield precisely the “unintended breadth” that use of the maxim properly prevents.
The structure and history of the Act confirm this reading. The ESA pursues its conservation purposes through three basic mechanisms: (1) a federal land acquisition program, ESA § 5,16 U.S.C. § 1534; (2) the imposition of strict obligations on federal agencies to avoid adverse impacts on endangered species, ESA § 7, 16 U.S.C. § 1536; and (3) a prohibition on the taking of endangered species by anybody, ESA § 9, 16 U.S.C. § 1538. The Act addresses habitat preservation in two ways — the federal land acquisition program and the directive to federal agencies to avoid adverse impacts. The latter frames the duty in terms that the Service has now transposed to the private anti-“take” provision: every such agency is to “insure that any action authorized, funded, or carried out by such agency ... is not likely to jeopardize the continued existence of any endangered species or threatened species or result in the destruction or adverse modification of habitat of such species which is determined ... to be critical”, unless an exemption is granted. 16 U.S.C. § 1536(a)(2) (emphasis added). Thus, on a specific segment of society, the federal government, the Act imposes very broad burdens, including the avoidance of adverse habitat modifications; on a broad segment, every person, it imposes relatively narrow ones.
The legislative history reflects this balance, and confirms the intention to assign the primary task of habitat preservation to the government. Explaining the land acquisition program, Senator Tunney, the Senate floor manager for the ESA, stated: “Through these land acquisition provisions, we will be able to conserve habitats necessary to protect fish and wildlife from further destruction.” 119 Cong.Rec. 25669 (July 24, 1973). Representative Sullivan, the floor manager for H.R. 37 — the House version of the bill— confirmed this approach:
For the most part, the principal threat to animals stems from the destruction of their habitat. The destruction may be intentional, as would be the case in clearing of fields and forests for development of resource extraction, or it may be unintentional, as in the case of the spread of pesticides beyond their target area. Whether it is intentional or not, however, the result is unfortunate for the species of animals that depend on that habitat, most of whom are already living on the edge of survival. H.R. 37 will meet this problem by providing funds for acquisition of critical habitat through the use of the land and water conservation fund. It will also enable the Department of Agriculture to cooperate with willing landowners who desire to assist in the protection of endangered species, but who are understandably unwilling to do so at excessive cost to themselves.
119 Cong.Rec. 30162 (Sept. 18,1973) (emphasis added). For habitat modification, then, Representative Sullivan saw the Act as providing duties for the government, with private persons acting only in the form of “willing landowners” assisted by the Department of Agriculture.
The floor managers differentiated loss of habitat from the hazard that was the target of the “taking” ban and the other prohibitions of § 9. After the passage quoted, Representative Sullivan went on to identify “[ajnother hazard to endangered species” which “arises from those who would capture or kill them for pleasure or profit. There is no way that the Congress can make it less pleasurable for a person to take an animal, but we can certainly make it less profitable for them to do so.” Id. (emphasis added). Senator Tunney drew the same line:
Although most endangered species are threatened primarily by the destruction of their natural habitats, a significant portion of these animals are subject to predation [1467]*1467by man for commercial, sport, consumption, or other purposes. The provisions in S. 1983 would prohibit the commerce in or the importation, exportation, or taking of endangered species except where permitted by the Secretary.
119 Cong.Rec. 25669 (July 24, 1973) (emphasis added).
Congress’s deliberate deletion of habitat modification from the definition of “take” strengthens our conclusion. As introduced before the Senate Commerce Committee, S. 1983 defined “take” as including “the destruction, modification, or curtailment of [a species’] habitat or range.” Endangered Species Act of 1973: Hearings on S. 1592 and S. 1983 Before the Subcomm. on Environment of the Senate Comm. on Commerce, 93d Cong., 1st Sess., at 27 (1973). A number of persons appearing before the Subcommittee on Environment explicitly endorsed this language and stressed its importance. See, e.g., testimony of John Grandy of the National Parks and Conservation Association, id. at 86; testimony of Tom Garrett, Wildlife Director of Friends of the Earth, id. at 104. Senators made the same point. See statement of Senator Moss, id. at 113; statement of Senator Williams, id. at 116. But the “take” definition of the version of S. 1983 submitted to the Senate omitted any reference to habitat modification, defining “take” to mean “harass, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.” See 119 Cong. Rec. 25663 (July 24, 1973). In rejecting the Service’s understanding of “take” to encompass habitat modification, “we are mindful that Congress had before it, but failed to pass, just such a scheme.” John Hancock Mutual Life Insurance Co. v. Harris Trust & Savings Bank, — U.S. -, -, 114 S.Ct. 517, 526, 126 L.Ed.2d 524 (1993).
The effect of the 1982 amendments
Congress amended the Act in 1982, with two possible implications. First, one might argue that one of the amendments so altered the context of the definition of “take” as to render the Service’s interpretation reasonable, or even, conceivably, to reflect express congressional adoption of that view. Second, one might argue that the process of amendment, which brought the Service’s regulation and a judicial endorsement to the attention of a congressional subcommittee, constituted a ratification of the regulation. We reject both theories.
1. The only legislative act from which the government claims support is the addition of ESA § 10(a)(1)(B), 16 U.S.C. § 1539(a)(1)(B), which authorizes the FWS to issue permits for “any taking otherwise prohibited by section 1538(a)(1)(B) of this title if such taking is incidental to, and not the purpose of, the carrying out of an otherwise lawful activity.” This language clearly implies that some prohibited takings are “incidental” to otherwise lawful activities. It does not follow, however, that such incidental takings include the habitat modifications embraced by the Service’s definition of “harm”. Harms involving the direct applications of force that characterize the nine other verbs of § 1532(19) pose the problem of incidental takings. The trapping of a nonendangered animal, for example, may incidentally trap an endangered species.
In fact, the key example of the sort of problem to be corrected by § 10(a)(1)(B) involved the immediate destruction of animals that would be trapped by a human enterprise. Northeast Utilities reported that it had sought to construct a nuclear plant on the Connecticut River. Dr. John P. Cagnet-ta explained on behalf of Northeast that the “EPA had concluded that Section 9 of the Act constituted a ‘zero taking* rule which would prohibit the entrainment or impingement of any Shortnose Sturgeon eggs, larvae or adults by the Montague intake structure.” Endangered Species Act of 1973: Hearings Before the Subcomm. on Fisheries and Wildlife Conservation and the Environment of the House Comm, on Merchant Marine and Fisheries (“Hearings”), 97th Cong., 2d Sess., at 358 (1982) (emphasis added). The “entrainment” and “impingement” of sturgeon eggs involve the crushing or capture of the eggs as a direct result of a human enterprise, just as would nets that catch fish driven in their way by the tides.
The sort of advance conservation plan authorized by § 10(a) makes complete sense for the kind of incidental taking exemplified by [1468]*1468Northeast’s dilemma. Dr. Cagnetta expressed concern that after the firm had invested $2 billion in the proposed plant, it might be subject to closure by injunction granted at the behest of a private person. Id. at 359. Section 10(a) provides procedural means by which to improve the trade-off between protecting endangered species and permitting normal development. Firms whose activities might incidentally “take” members of an endangered species can get advance protection from legal liability, but only if they convince the Secretary that the plan uses the maximum devices possible to mitigate and minimize species loss, and that the resulting losses will not unduly harm the species. See § 10(a)(2)(B)(ii) & (iv), 16 U.S.C. § 1539(a)(2)(B)(ii) & (iv).
Thus, adoption of § 10(a)’s permit plan, at least as evidenced by Northeast’s instigating role, arose from interpretive assumptions about the meaning of “taking”— namely the EPA’s views (1) that the perpetrator need not have intended to take the creature in question, and (2) that even the slightest taking would violate the Act (the “zero taking” rule). We need not explore the possible impact of these assumptions on the interpretation of “take”; a member of Congress might have supported the permit system on a completely agnostic premise about those interpretations: “There are some pretty wild interpretations out there, and they may stick; if they do, it would certainly be helpful to have a mechanism for softening their impact.” Normally, erroneous legislative assumptions about the meaning of an existing statute, even when they serve as the premise of an amendment, do not alter the meaning of unamended provisions. See Mackey v. Lanier Collection Agency & Serv., 486 U.S. 825, 840, 108 S.Ct. 2182, 2191, 100 L.Ed.2d 836 (1988). Here, however, the matter is even easier, as the amendment involved no assumptions supporting the Service’s position on habitat modification. So far as the creation of the permit plan is concerned, the implicit assumptions simply do not embrace the idea that “take” included any significant habitat modification injurious to wildlife.
2. For its ratification theory, the government invokes (besides the § 10(a)(2) amendment itself) (a) language in the Conference on the 1982 amendments; (b) notice to a House subcommittee of the Service’s habitat modification regulation and of a decision upholding it; and (c) the decision of a senator not to offer an amendment. We first examine these and then consider the cases on ratification of mistaken interpretations, on the basis of congressional awareness and peripheral action.
(a) The Conference Report. The government highlights some observations of H.R.Rep. No. 835, 97th Cong., 2d Sess. (1982) (“Conference Report”), 1982 U.S.C.C.AN. 2807, speaking of the innovation made by § 10(a):
This provision is modeled after a habitat conservation plan that has been developed by three Northern California cities, the County of San Mateo, and private landowners and developers to provide for the conservation of the habitat of three endangered species and other unlisted species of concern within the San Bruno Mountain area of San Mateo County.
This provision will measurably reduce conflicts under the Act and will provide the institutional framework to permit cooperation between the public and private sectors in the interest of endangered species and habitat conservation.
The terms of this provision require a unique partnership between the public and private sectors in the interest of species and habitat conservation_
Id. at 30-31, reprinted in 1982 U.S.C.C.AN. 2871-72 (emphasis added).
Although the passage thrice uses the phrase “habitat conservation”, the first reference simply describes the particular plan on which the provision was modeled, while the second and third couple the phrase with, respectively, “the interest of endangered species” and “the interest of species.” The focus is on the flexibility of the relief offered. The expectation that relief under the § 10(a) permit scheme would include habitat conservation does not imply an assumption that takings encompass habitat modification. Thus, if a nuclear plant will “entrain” and “impinge” sturgeon eggs, the area where this occurs will certainly not be hospitable for the [1469]*1469sturgeon, and mitigation measures invited by § 10(a) might well include provision of alternative habitat. Similarly, although § 10(a) relief contemplates advancing “the interest of endangered species”, it does not follow that every act detrimental to an endangered species constitutes a forbidden taking.
(b) Notice of the regulation. The Subcommittee on Fisheries and Wildlife Conservation and the Environment of the House Committee on Merchant Marine and Fisheries had notice of the regulation. See, e.g., Hearings at 290. In addition, speakers brought a decision of the 9th Circuit upholding the application of the ESA to habitat modification, Palila v. Hawaii Dep’t of Land & Natural Resources, 639 F.2d 495 (9th Cir.1981), to the attention of subcommittee members in attendance. See Hearings at 329, 331. See also id. at 331, 426 (expressions of conflicting views on validity of interpretation of “harm” to encompass habitat modification). So far as appears, no congressional awareness of the Service’s regulation or of Palila reached the floor of either House.
(c) The withdrawn amendment. The government says that Senator Garn proposed an amendment to change the definition of “take” but “withdrew it voluntarily because he realized it did not have enough support for passage.” Appellee Brief at 32. This falsely suggests a focus on “habitat modification” that was simply not there. In fact, the amendment that Senator Garn withdrew was not an isolated redefinition of the term “take”, but a wholesale “rewrite” of the ESA3 — the reading of which was dispensed with on the Senate floor, and the text of which took 16 dense pages of legislative history. A Legislative History of the Endangered Species Act of 1973, As Amended in 1976, 1977, 1978, 1979, and 1980 (U.S.Govt.1982) at 1080. The record reveals nothing to suggest any relation between Senator Garn’s decision and congressional sentiment on the habitat modification issue.
By what standard are these features of the 1982 amendment process to be evaluated? Although the precedents are hardly in perfect harmony, the Supreme Court has generally refused to infer ratification from mere amendment of adjacent clauses in these circumstances. It has forcefully articulated reasons for this refusal. In Girouard v. United States, 328 U.S. 61, 66 S.Ct. 826, 90 L.Ed. 1084 (1946), the Court concluded that it had erred in three prior cases holding that an alien who refused to bear arms could not be admitted to citizenship under the terms of the oath prescribed by Congress for naturalization. Id. at 61-69, 66 S.Ct. at 826-830. It then confronted a claim that Congress had impliedly adopted the rule of the earlier decisions, a claim to which the facts lent considerable support — unsuccessful efforts to change the rule, plus reenactment of the underlying language amid change of many related provisions. Id. at 69, 66 S.Ct. at 829 (emphasis added).
In dissent, Chief Justice Stone set out the principle that where a statutory provision has been subject to a controversial construction, reenactment without change implies congressional approval of that construction. Id. at 76, 66 S.Ct. at 833 (Stone, C.J., dissenting). The court, however, rejected this approach, and warned “[i]t is at best treacherous to find in congressional silence alone the adoption of a controlling rule of law.” Id. at 69, 66 S.Ct. at 830. It observed that congressional silence and inaction — actually, reenactment of the pertinent language — were “as consistent with a desire to leave the problem fluid as they are with an adoption by silence of the rule of [the prior] cases.” Id. at 70, 66 S.Ct. at 830.
Similarly, where Congress adopts amendments on the basis of a misconception as to the meaning of a prior statute’s related provisions, the later act does not turn the misconception into law. Mackey v. Lanier Col[1470]*1470lection Agency & Serv., 486 U.S. 825, 108 S.Ct. 2182, 100 L.Ed.2d 836 (1988), illustrates the principle. As originally enacted, the Employee Retirement Income Security Act (“ERISA”) preempted state laws “as they may now or hereafter relate to any employee benefit plan” covered by the statute. ERISA § 514(a), 29 U.S.C. § 1144(a). After a number of lower courts construed § 514(a) to preempt state garnishment statutes, Congress in 1984 expanded the statutory list of exceptions to § 514(a), adding garnishments in support of domestic relations orders and thereby expressly eliminating ERISA’s preemption of that narrow category. See ERISA § -514(b)(7), 29 U.S.C. § 1144(b)(7). Though the Court recognized that language in the House Committee report “suggest[ed] that the House Committee in 1984 thought that § 514(a) foreclosed state-law attachment orders akin to those at issue here”, id. at 840, 108 S.Ct. at 2191, i.e., garnishments outside the area of domestic relations, it refused to attach weight to that implicit suggestion. Rather, the Court said that “these views— absent an amendment to the original language of the section — do not direct our resolution of this case. Instead, we must look at the language of ERISA and its structure, to determine the intent of the Congress that originally enacted the provision in question. ‘It is the intent of the Congress that enacted [the section] ... that controls.’ Teamsters v. United States, 431 U.S. 324, 354, n. 39, 97 S.Ct. 1843, 1864 n. 39, 52 L.Ed.2d 396 (1977).” Id.
And in Shearson/American Express Inc. v. McMahon, 482 U.S. 220, 107 S.Ct. 2332, 96 L.Ed.2d 185 (1987), the Supreme Court refused to find implied ratification even though Congress amended closely related statutory sections and the Conference Report appeared to support the prevailing interpretation. The Court had, in Wilko v. Swan, 346 U.S. 427, 74 S.Ct. 182, 98 L.Ed. 168 (1953), construed certain provisions of the Securities Act of 1933 to bar enforcement of pre-dispute agreements to arbitrate for disputes under § 12(2) of that act, despite the broad endorsement of arbitration in the previously adopted Federal Arbitration Act, 9 U.S.C. § 1 et seq. The issue in Shearson/American Express was whether similar provisions in the Securities Exchange Act of 1934 prevented enforcement of a pre-dispute arbitration agreement as to an alleged violation of § 10(b) of that Act, as the circuit courts of appeal had generally held.
After finding that the 1934 Act as originally enacted created no exception to the Arbitration Act, the Court turned to whether a later congressional intervention, the 1975 amendments to both the 1933 and the 1934 Acts — “the ‘most substantial and significant revision of this country’s Federal securities laws since the passage of the Securities Exchange Act in 1934'”, Shearson/American Express, 482 U.S. at 246, 107 S.Ct. at 2347 (Blackmun, J., dissenting) — altered that result. The 1975 amendments included a change in a section of the 1934 Act (§ 28(b)) closely related to those sections from which lower courts had drawn the inference against pre-dispute arbitration clauses, and the Conference Report had in connection with that change virtually endorsed Wilko v. Swan:
It was the clear understanding of the conferees that this amendment did not change existing law, as articulated in Wilko v. Swan, 346 U.S. 427 [74 S.Ct. 182, 98 L.Ed. 168] (1953), concerning the effect of arbitration proceedings provisions in agreements entered into by persons dealing with members and participants of self-regulatory organizations.
H.R.Conf.Rep. No. 94-229 at 111 (1975), 1975 U.S.C.C.AN. pp. 179, 342 (1975) (quoted at Shearson/American Express, 482 U.S. at 236-37, 107 S.Ct. at 2343).
To Justice Blackmun, dissenting for himself and Justices Brennan and Marshall, this showed that Congress was clearly aware of the extension of Wilko to the 1934 Act and, at a minimum, that it was “not concerned with arresting this trend.” 482 U.S. at 247, 107 S.Ct. at 2348. But the majority, although finding some ambiguities in the remarks of the Conference Report, stressed the absence of any affirmative action by Congress in regard to the controlling sections: “We cannot see how Congress could extend Wilko to the [1934] Act without enacting into law any provision remotely addressing that subject.” Id. at 237, 107 S.Ct. at 2343.
[1471]*1471A variant on this theme is TVA v. Hill, 437 U.S. 153, 98 S.Ct. 2279, 57 L.Ed.2d 117 (1978), involving claims that Congress’s several appropriations for the Tellico Dam, made with full awareness of its risks to the snail darter and with express statements in various House and Senate Appropriations Committees’ reports that the ESA was not meant to apply to this project, effectively exempted the dam from § 7 of the Act. Despite Congress’s endorsement of the disputed project with the ultimate accolade — hard cash — the Court refused to find any exemption. Id. at 189-93, 98 S.Ct. at 2299-2301. The Court underscored the proposition that only congressional committees had expressed the understanding of § 7 that contradicted the Court’s reading. Id. at 189, 193, 98 S.Ct. at 2299, 2301.
Our own decision in State of Ohio v. U.S. Department of the Interior, 880 F.2d 432 (D.C.Cir.1989), elaborates on the jurisprudential concerns raised by Shearson/American Express. The court considered a situation where Congress had amended the key sections being construed and had reenacted the entire statute. Judge Wald wrote for the court:
Were we to infer congressional approval of Interior’s rules because it did not amend the statute to explicitly repudiate them, we would in effect be insisting that a Congress legislatively reiterate an already clear statutory command in order to fend off an impermissible interpretation. As we all know, many statutes are on the books for which no congressional majority could presently be garnered either to reenact or to repeal, yet those acts continue as valid law; indeed, a canon of equal worth with the acquiescence-by-reenactment rule is the one disfavoring repeal by implication. We conclude that the acquiescence-by-re-enaetment rule is not applicable to a situation where the regulations violate the original statutory language and where Congress’ decision not to amend the relevant statutory provisions evidently stems from a belief that the provisions have been clear all along.
Id. at 458-59. Although the court evidently understood congressional inaction to stem from a belief that the statute had been “clear all along” (against the administrative interpretation), the ambiguity we pinpointed is relevant more broadly. Congressional inaction may indicate no more than the press of other business. As inaction is inadequate to repeal a law, it should be inadequate to modify a law. Yet modification is required to sustain an interpretation that is invalid as against the original legislation. Professor Tribe has pointed out that judicial reliance on congressional silence generates an elaborate buck-passing. The courts pass the buck to Congress by invoking the congressional inaction, and individual members of Congress can freely pass the buck back by pointing to the courts’ action. See Laurence H. Tribe, Constitutional Choices 33-34 (1985).
We do not pretend that the Court’s treats ment of this issue has been absolutely uniform. There are cases indicating some readiness to infer ratification merely from amendment of related provisions (coupled with acute congressional focus on outstanding interpretations), and even from mere notice followed by inaction. In United States v. Riverside Bayview Homes, Inc., 474 U.S. 121, 106 S.Ct. 455, 88 L.Ed.2d 419 (1985), for example, the Court considered the Corps of Engineers’ broad reading of “waters of the United States” in the 1972 Clean Water Act, and placed some weight on Congress’s 1977 failure — in the course of making important amendments and after extensive floor debate — to modify the Corps’s interpretation. “Although we are chary of attributing significance to Congress’ failure to act, a refusal by Congress to overrule an agency’s construction of legislation is at least some evidence of the reasonableness of that construction, particularly where the administrative construction has been brought to Congress’ attention through legislation specifically designed to supplant it.” Id. at 137, 106 S.Ct. at 464. In Bob Jones University v. United States, 461 U.S. 574, 103 S.Ct. 2017, 76 L.Ed.2d 157 (1983), the Court attached weight to the fact of Congress’s awareness of IRS rulings that barred tax-exempt status for racially discriminatory schools, noting that 13 bills had been introduced over the years to overturn the rulings, none ever emerging from committee. Id. at 600, 103 S.Ct. at 2033. But the Court [1472]*1472also observed that “[njonaction by Congress is not often a useful guide”. Id. More important, perhaps, Congress itself had, over the same period, adopted anti-discrimination prerequisites for private club exemptions, a closely parallel issue with obvious implications for the meaning of the general language exempting charitable and educational institutions. Id. at 601-02, 103 S.Ct. at 2033-34. And in Commodity Futures Trading Comm’n v. Schor, 478 U.S. 833, 106 S.Ct. 3246, 92 L.Ed.2d 675 (1986), the Court broadly suggested that congressional “revisit[ations]” of a statute after a longstanding administrative interpretation, coupled with failure to modify the interpretation, suggested support for the agency view. Id. at 846, 106 S.Ct. at 3254. But in Schor the Court found the rejected reading of the statute inconsistent with the statutory language, id. at 841-42, 106 S.Ct. at 3251-52, and fraught with incongruities, see id. at 843-44, 106 S.Ct. at 3252-53, and also read the later amendments as “explicitly affirm[ing]” the agency’s view, id. at 846, 106 S.Ct. at 3254.
These cases may ultimately not be fully reconcilable. We note, however, that the cases drawing inferences from inaction typically fail to address the serious jurisprudential problems of doing so — especially those captured in Judge Wald’s observation that there are plenty of statutes “on the books for which no congressional majority could presently be garnered either to reenact or to repeal”. State of Ohio, 880 F.2d at 458. It hardly seems consistent to enforce such statutes yet to accept non-amendment of an interpretation as the equivalent of congressional endorsement.
If the 1982 Congress had reenacted the pertinent sections of the ESA and “voice[d] its approval” of the FWS’s interpretation, it might be appropriate to treat the reenactment as an adoption of that interpretation. United States v. Bd. of Commissioners, 435 U.S. 110, 134, 98 S.Ct. 965, 980, 55 L.Ed.2d 148 (1978). But see Girouard. Here, however, Congress neither reenacted the sections having to do with “take”, nor “voiced its approval” of the harm regulation. As we have seen, its creation of the permit scheme is fully consistent with the meaning of “take” as enacted in 1973; the other developments show no more than awareness of the Service’s view, its survival in Palila, and the absence of any action to endorse or repudiate those developments.
Accordingly, we hold invalid the Fish & Wildlife Service regulation defining “harm” to embrace habitat modifications. The judgment of the district court is reversed to that extent; otherwise, the judgment of this court in Sweet Home Chapter v. Babbitt, 1 F.3d 1 (D.C.Cir.1993), is unaltered.
So ordered.