OPINIONS EN BANC
SELYA, Circuit Judge.
Almost two decades ago, Gail Merchant Irving suffered horrific injuries in a workplace accident. She sued the United States under the Federal Tort Claims Act (FTCA), 28 U.S.C. §§ 1346(b), 2671-2680, claiming that inspectors employed by the Occupational Safety and Health Administration (OSHA) negligently performed their duties and thereby proximately caused her injuries. The case traveled an inexcusably long and tortuous route to a decision on the merits — a route that included four detours to this court. Ultimately, the district court, proceeding under a legal framework established by a panel of this court, concluded that the FTCA’s discretionary function exception did not bar the plaintiffs claim; that the OSHA inspectors had acted negligently; and that such negligence was actionable under applicable state law. See Irving v. United States, 942 F.Supp. 1483 (D.N.H.1996) (Irving III). The court awarded the plaintiff $1,000,000 in damages. See id. at 1502.
A divided panel of this court affirmed the judgment, see Irving v. United States, 1998 WL 152941 (1st Cir. Apr. 8, 1998), but the full court, acting sua sponte, withdrew the opinion and ordered rehearing en banc, principally to review the important question of whether the FTCA’s discretionary function exception foreclosed the plaintiffs negligent inspection claim. We now answer that question in the affirmative.1
I. BACKGROUND
Because the district court has faithfully chronicled the tangled events that preceded this appeal, see Irving III, 942 F.Supp. at 1485-98, we offer only a synopsis. We refer the reader who hungers for greater detail to the district court’s account.
In 1979, Somersworth Shoe Company operated a manufacturing plant in New Hampshire. On October 10 of that year, the plaintiff, a Somersworth Shoe employee, was stamping innersoles by means of a marker machine. At one point, she went behind her workbench to obtain materials from the die rack. In the process, she dropped a glove. [158]*158When she stooped to retrieve it, her hair was drawn into the vacuum created by the high-speed rotation of a drive shaft that delivered power to an adjacent “die-out” machine. She sustained grievous injuries.
OSHA compliance officers twice had inspected the plant (once in 1975 and again in 1978) under the auspices of OSHA’s authority to conduct general administrative inspections, but had not noted any hazard in connection with the placement or guarding of the die-out machine in the stock fitting room or the bench assembly associated with it. Six days after Irving’s mishap, OSHA conducted an inspection focused on the accident and concluded that the arrangement violated OSHA standards in three separate respects, and that all three conditions were “serious.”2 The most important of these was the company’s failure to guard the drive shaft component of the die-out machine. See 29 C.F.R. § 1910.219(c)(2)(ii) (“Shafting under bench machines shall be enclosed by a stationary easing, or by a trough at sides and top or sides and bottom, as location requires.”).
After exhausting her administrative remedies, the plaintiff invoked the FTCA and sued the United States in New Hampshire’s federal district court. She alleged that OSHA’s negligence in failing to note and cite the unguarded condition of the drive shaft during the two pre-accident inspections proximately caused her injuries. Had the OSHA compliance officers documented the condition of the die-out machine, the plaintiff reasoned, her employer would have taken corrective action and her injury would not have occurred.
The United States moved to dismiss the suit on the ground that the FTCA’s discretionary function exception barred the plaintiffs claim.3 The district court denied the motion. See Irving v. United States, 532 F.Supp. 840 (D.N.H.1982). Trial commenced on February 11, 1985, and ended three days later. The district court took the matter under advisement, but did not act for almost three years. At that point, the court reversed its field and concluded that the discretionary function exception applied after all. See Irving v. United States, No. Civ. C81-501-SD, slip op. (D.N.H. Jan. 27, 1988) (unpublished). Accordingly, it dismissed the case for lack of subject matter jurisdiction.
A panel of this court vacated the order of dismissal and asked the district court to consider the impact of a newly decided case, namely, Berkovitz v. United States, 486 U.S. 531, 108 S.Ct. 1954, 100 L.Ed.2d 531 (1988). See Irving v. United States, 867 F.2d 606 (1st Cir.1988) (table). The district court determined that Berkovitz did not alter the result. See Irving v. United States, No. Civ. C81-501-SD, slip op. (D.N.H. Feb. 14, 1989) (unpublished). The plaintiff again appealed.
A second panel of this court vacated the judgment. See Irving v. United States, 909 F.2d 598 (1st Cir.1990) (Irving I). The panel recognized that, “[wjere the statute and the formal regulations the only standards guiding the compliance officer’s conduct, the discretionary function exception would apply.” Id. at 603. But, the panel stated, even though these standards “give OSHA wide freedom at higher agency levels to make decisions and formulate programs,” it “does not follow” that “an employee who performs an inspection has the type and breadth of discretion which makes the inspection a discretionary function.” Id. The panel thus concluded that further analysis and factfinding were required to determine what OSHA policy actually required of OSHA compliance officers engaged in inspection activities. See id. As a corollary to this point, the panel noted that certain statements by OSHA’s area director and the individuals who conducted the earlier inspections suggested that compliance officers may not have enjoyed discretion over how thoroughly they were [159]*159required to inspect a plant. See id. at 604-05. Because these statements were inconclusive, however, the panel remanded for further factfinding to determine “whether OSHA policy left the thoroughness of inspections a matter of choice for its compliance officers,” and if so, “whether the inspectors had policy-level discretion to fail to note and tell the employer about the violation” which allegedly caused plaintiffs injury. Id. at 605.
The district court pondered matters for four more years. Eventually, the judge, relying on a partial transcript of the 1985 trial, supplemented by his own notes, leapfrogged the discretionary function exception entirely and decided the case on the merits, concluding that the United States was not negligent because the die-out machine’s drive shaft was “guarded by location” at the time of the inspections and, therefore, in full compliance with OSHA regulations. Irving v. United States, No. Civ. 81-501-SD, 1994 WL 287750, at *3 (D.N.H. June 23, 1994). The plaintiff again appealed.
A third panel of this court vacated the judgment, discerning no basis for the “guarded by location” fact determination. See Irving v. United States, 49 F.3d 830, 835-37 (1st Cir.1995) (Irving II). The panel then addressed the government’s attempted resurrection of its discretionary function defense and rejected it as foreclosed by the prior panel decision. See id. at 834 (noting that the panel did not feel “free to revisit” the legal conclusions explicated in Irving I). In the bargain, the panel dismissed the government’s plaint that the Supreme Court’s intervening decision in United States v. Gaubert, 499 U.S. 315, 111 S.Ct. 1267, 113 L.Ed.2d 335 (1991), made a decisive difference. See Irving II, 49 F.3d at 834-35.
At this juncture, a different trial judge assumed responsibility for the case. Operating within the legal framework erected by Irving I and reinforced by Irving II, the district court concluded that, even though the applicable statute, regulations, and written agency guidelines appeared to grant compliance officers substantial discretion over how to conduct inspections, this discretion was restricted “by less formal, but no less binding, OSHA policy.” Irving III, 942 F.Supp. at 1490-91. To determine the parameters of this purported policy, the district court relied exclusively on evidence adduced at the 1985 trial. It found that the testimony of the compliance officers who had conducted the 1975 and 1978 inspections and tbe area director who was their superior limned a policy that “required” OSHA’s “wall-to-wall” inspections to be “complete” in every respect. Id. at 1491. This, the district court added, meant that OSHA inspectors were obligated to examine “every operational machine and work station in the plant.” Id. Finding that the inspectors had been negligent for not examining and/or citing the die-out machine, the court held that the United States was liable. See id. at 1505, 1510. This appeal ensued.
II. PROCEDURAL ISSUES
Because this case comes before us in an anomalous procedural posture, we begin by addressing a series of questions related to the justiciability of the discretionary function issue.
A. Forfeiture.
When the United States instituted this appeal, it did not ask the panel to reverse the district court’s refusal to apply the discretionary function exception. The plaintiff now seeks to convince us that this omission precludes the en bane court from considering the issue. We are not persuaded.
In the ordinary course, a party seeking to preserve a point for review must present it seasonably in both the trial and appellate courts and offer developed argumentation in support. See, e.g., United States v. Bongiorno, 106 F.3d 1027, 1034 (1st Cir.1997). Thus, a party who fails to raise a particular claim or defense at a prior stage in the litigation normally forfeits the right to assert it at a later stage. See National Ass’n of Soc. Workers v. Harwood, 69 F.3d 622, 627-29 (1st Cir.1995). But the instant case does not fit this paradigm neatly. Even though the United States did not hawk its basic discretionary function defense the last time around, it did assert the defense at the very beginning of this case and persistently [160]*160raised it thereafter. It was not until the final round of litigation that the government put down those cudgels.
The United States had good reason not to press its basic discretionary function point at that stage (either in the district court or before the fourth appellate panel). In Irving I, a panel of this court expressly defined the contours of the discretionary function exception. 909 F.2d at 601-05. From then on, that methodology represented both the law of the ease and the law of this circuit regarding the due application of the discretionary function exception. The law of the circuit doctrine, as a general matter, permits successor panels to revise prior panel decisions in only two types of circumstances: (1) when supervening authority (such as a newly enacted statute, an intervening opinion of the Supreme Court, or a subsequent ruling of the en banc court) directly requires such a step, or (2) when newly emergent authority, though not controlling, offers a clear and convincing reason to conclude that the earlier panel would have decided the issue differently. See Williams v. Ashland Eng’g Co., 45 F.3d 588, 592 (1st Cir.1995). Indeed, when the United States asserted the discretionary function defense in Irving II, the panel not only took refuge in the law of the circuit doctrine to dispense the argument, but also rejected the government’s importuning that the Supreme Court’s 1991 decision in Gaubert required a modification of the prior circuit precedent. See Irving II, 49 F.3d at 834-35. Because two panels of this court had squarely rebuffed the government’s discretionary function defense, it is hardly surprising that the government did not raise it anew in subsequent proceedings before yet another (co-equal) panel of this court. See Louisiana-Pacific Corp. v. ASARCO, Inc., 24 F.3d 1565, 1583 (9th Cir.1994) (stating that raising a point on appeal that governing state law foreclosed would have been “foolish,” and excusing waiver); see also United States v. London, 66 F.3d 1227, 1239-240 (1st Cir.1995).
In sum, strong arguments can be made for not finding a forfeiture here or, at least, for not strictly applying forfeiture principles. Still, we need not definitively decide the point, for there is a simple, clearcut answer to whether the question is properly before us. After all, the discretionary function exception to the FTCA implicates the federal courts’ subject matter jurisdiction. Federal courts, being courts of limited jurisdiction, have an affirmative obligation to examine jurisdictional concerns on their own initiative. See BIW Deceived v. Local S6, Indus. Union of Marine & Shipbuilding Workers, 132 F.3d 824, 828 (1st Cir.1997). Consequently, even if the government failed properly to raise and preserve the discretionary function defense — a question on which we take no view — we nonetheless are bound to consider it.4 See Hydrogen Technology Corp. v. United States, 831 F.2d 1155, 1162 n. 6 (1st Cir.1987).
In her supplemental brief, the plaintiff puts a somewhat different spin on the forfeiture argument. Citing a footnote in the final district court opinion, she argues that the government conceded the discretionary function question in that venue by admitting that OSHA policy required its compliance officers to “inspect every operation”. Irving III, 942 F.Supp. at 1491 n. 8. Waiver is, of course, a matter separate from forfeiture. See United States v. Olano, 507 U.S. 725, 733, 113 S.Ct. 1770, 123 L.Ed.2d 508 (1993). Be that as it may, we have reviewed the record with care and can find no such concession.5 In any event, insofar as the plaintiff [161]*161asserts that the United States has conceded the discretionary function issue, we note that parties do not possess the power to confer subject matter jurisdiction on a federal court by concession.6 See United States v. Horn, 29 F.3d 754, 768 (1st Cir.1994).
B. Power of the En Banc Court.
The procedural tangle in this case raises yet another question: may an en banc court review issues decided by panels of the court in prior appeals in the same litigation? We hold that neither the law of the case doctrine nor the law of the circuit doctrine disables an en banc court from overruling a panel decision from a prior appeal in the same case. Accord Watkins v. United States Army, 875 F.2d 699, 704-05 n. 8 (9th Cir. 1989) (en bane); Shimman v. International Union of Operating Eng’rs, Local 18, 744 F.2d 1226, 1229 n. 3 (6th Cir.1984) (en banc). The authority to overrule the decision of a prior panel in the same case flows logically from the eiTor-correeting function of the full court. When a court sits en banc, the concern for adhering to a past resolution of an issue in deference to settled expectations, which underpins the doctrines of law of the case and law of the circuit, must give way to the institutional interest in correcting a precedent-setting error of great public import or a panel opinion that conflicts with Supreme Court precedent. See United States v. Rivera-Martinez, 931 F.2d 148, 151 (1st Cir. 1991) (noting that law of the case doctrine does not apply when “controlling authority has since made a contrary decision of the law applicable”) (internal quotes and citations omitted); see also Irving II, 49 F.3d at 834 (acknowledging that the law of the circuit rule would not apply in the face of a contrary en banc opinion).
We are aware that the Eighth Circuit appears to have suggested otherwise. See Robertson Oil Co. v. Phillips Petroleum Co., 14 F.3d 373 (8th Cir.1993) (en banc). The Robertson majority held that the law of the case doctrine precluded it from revisiting holdings from two earlier panel decisions because the full court had denied contemporaneous suggestions for en banc rehearings after the adjudication of both the first and second appeals. See id. at 376 n. 5, 383, & n. 13. We decline to follow Robertson for two reasons. First, in this case, unlike in Robertson, the en banc court was not invited to review any of the earlier panel decisions on a contemporaneous basis, and thus, did not decline to do so.7 Second — and more important — to the extent that the Robertson majority’s reasoning rests on mechanically applying the law of the case doctrine to the decisions of earlier panels across the board, it too narrowly cabins the proper purview of a court sitting en banc. See id. at 386-88 (Beam, J., with whom Bowman and Loken, JJ., join, dissenting).
[162]*162Nor does the decision in Van Gemert v. Boeing Co., 590 F.2d 433 (2d Cir.1978) (en banc), create an obstacle to en banc review of a prior panel decision. There, the Second Circuit suggested that the en banc court is free to overturn prior panel decisions unless doing so would seriously and unfairly prejudice the party that had benefitted from the earlier ruling. See id. at 436-37 n. 9 (stating in dictum that “sitting en banc, we may overrule any panel decision that a majority of the active judges believes was wrongly decided, unless a party would be seriously prejudiced as a result”). Even were we prepared to adopt this formulation of the rule — a matter which we leave for another day — it would not preclude us from reviewing the holdings of Irving I and Irving II. As we have noted, the discretionary function exception implicates the subject matter jurisdiction of federal courts. Prejudice to a party, while always regrettable, cannot furnish a viable rationale for overlooking a federal court’s lack of power to grant a remedy in the first place.
III. THE DISCRETIONARY FUNCTION EXCEPTION
Having cut a swath through the procedural thicket, we turn to the government’s discretionary function defense. In the process, we afford plenary review to the question of whether the discretionary function exception applies. See National Union Fire Ins. v. United States, 115 F.3d 1415, 1417-18 (9th Cir.1997), cert. denied, — U.S. -, 118 S.Ct. 1053, 140 L.Ed.2d 116 (1998); Fisher Bros. Sales, Inc. v. United States, 46 F.3d 279, 282 (3d Cir.1995) (en banc).
In the Court’s words, “the basic inquiry concerning the application of the discretionary function exception is whether the challenged acts of a Government employee— whatever his or her rank — are of the nature and quality that Congress intended to shield from tort liability.” United States v. S.A. Empresa de Viacao Aerea Rio Grandense (Varig Airlines), 467 U.S. 797, 813, 104 S.Ct. 2755, 81 L.Ed.2d 660 (1984). To respond to this inquiry, we first must identify the conduct at issue and then determine whether that conduct is discretionary. See Gaubert, 499 U.S. at 322, 111 S.Ct. 1267. Even if this hurdle is cleared, the discretionary function exception still does not attach unless the exercise of discretion involves (or, at least, is susceptible to) policy-related judgments. See id. at 322-23, 111 S.Ct. 1267.
A. The Statutory and Regulatory Regime.
In this instance, the plaintiff claims that workplace inspections, negligently performed by OSHA compliance officers, proximately caused her injuries. In analyzing the nature of this conduct, we begin with the language of the OSH Act because “it will most often be true that the general aims and policies of the controlling statute will be evident from its text,” id. at 324, 111 S.Ct. 1267, and, in turn, these aims and policies will offer valuable insights into the nature of the conduct.
In relevant part, the OSH Act authorizes the Secretary of Labor to “inspect and investigate during regular working hours and at other reasonable times, and within reasonable limits and in a reasonable manner, any such place of employment and all pertinent conditions, structures, machines, apparatus, devices, equipment, and materials therein....” 29 U.S.C. § 657(a). Under this authority, OSHA conducts both programmed general administrative inspections — known in the bureaucratic argot that OSHA so readily attracts as “full-scope” or “wall-to-wall” inspections — and more focused efforts pinpointed to threats of imminent danger.8 Aside from a reasonableness limitation on the time and manner of inspections, the statute places virtually no constraint on the Secretary’s discretion to conduct such inspec[163]*163tions in any way that she deems fit. See Donovan v. Dewey, 452 U.S. 594, 601, 101 S.Ct. 2534, 69 L.Ed.2d 262 (1981).
Comparison of this language to a parallel provision in the Federal Mine Safety and Health Act (MSH Act), 30 U.S.C. § 801 et seq., another health and safety statute administered by the Secretary of Labor, strongly suggests that Congress’s choice of words was no accident. In defining the Secretary’s responsibilities regarding mine inspections, the MSH Act provides that, in order to determine whether “an imminent danger exists” in a mine and “whether there is compliance with the mandatory health or safety standards or with a citation, order, or decision” issued under applicable law, “the Secretary shall make inspections of each underground coal or other mine in its entirety at least four times a year, and of each surface coal or other mine in its entirety at least two times a year.” 30 U.S.C. § 813(a) (emphasis supplied). For our purposes, the stark differences between the inspection provisions of the MSH Act and those of the OSH Act are extremely significant. Whereas Congress was careful to mandate comprehensive inspections in the MSH Act, it left the scope and detail of OSH Act inspections to the Secretary’s discretion. Had Congress wished to impose upon OSHA an obligation to inspect every corner of every plant that it visited, we think it is highly likely that Congress would have expressed its intention by choosing language comparable to that which it used in crafting the MSH Act.9
We recognize that, by its plain terms, the OSH Act confers discretion only upon the Secretary, not upon compliance officers — -and it is the latter’s conduct that concerns us. Nevertheless, the legislative rules governing the authority of compliance officers mimic the statute and grant these officials broad discretion over the scope, manner, and detail of general administrative inspections. The regulations’ stated goal is “to set forth general policies for enforcement of the inspection, citation, and proposed penalty provisions of the Act.” 29 C.F.R. § 1903.1. Echoing the language of 29 U.S.C. § 657(a), section 1903.3 of the regulations confers upon compliance officers the unbridled power, subject only to limits of reasonableness, to enter workplaces, inspect any piece of equipment or other pertinent item, and interview any person in order to carry out the Secretary’s statutory mission. See 29 C.F.R. § 1903.3(a).
To be sure, the regulations contain a sprinkling of mandatory directives. See, e.g., id. at § 1903.7 (obligating compliance officers, inter alia, to present their credentials at the start of an inspection, to use “reasonable precautions” when taking photographs and samples, to wear appropriate protective clothing, to avoid “unreasonable disruption” of the workplace, and to “confer with the employer” in order to inform him of “any apparent safety or health violations disclosed by the inspection”). Save for these and, for our purposes, other similarly innocuous details, the regulations neither mandate a particular modus operandi for conducting inspections nor otherwise materially restrict compliance officers’ flexibility. Of particular importance, the regulations do not prescribe any specific regimen governing the scope or detail of general administrative inspections performed by compliance officers.
B. The Nature of the Action.
Under the jurisprudence of the FTCA, a function is non-diseretionary only when a “federal statute, regulation, or policy specifically prescribes a course of action for an employee to follow.” Gaubert, 499 U.S. at 322, 111 S.Ct. 1267 (quoting Berkovitz, 486 U.S. at 536, 108 S.Ct. 1954); accord Williams [164]*164v. United States, 50 F.3d 299, 309-10 (4th Cir.1995) (applying discretionary function bar because applicable regulations did not mandate a specific course of action for agent to follow when engaging managerial and custodial services); Layton v. United States, 984 F.2d 1496, 1502-03 (8th Cir.1993) (holding that, in the absence of specific guidelines, the manner of inspection is a matter of discretion, and distinguishing situations “in which [a] government inspector is controlled by precise regulations establishing specific steps he is required to perform in his inspections”); Cooper v. American Auto. Ins. Co., 978 F.2d 602, 612 (10th Cir.1992) (holding that discretionary function exception bars negligent investigation claim absent any statute or “regulation mandating particular inquiries to be made or methods of making them”). Given the considerable leeway afforded to compliance officers under the statutory and regulatory mosaic, general administrative inspections conducted by OSHA compliance officers would seem to fit comfortably within the discretionary function exception. Indeed, two of our sister circuits have so held, see Judy v. United States, 864 F.2d 83, 84 (8th Cir.1988); Galvin v. OSHA, 860 F.2d 181, 184 (5th Cir.1988), and none has demurred.
The Irving I panel, though clearly recognizing the discretionary nature of the authority granted by the statute and regulations, 909 F.2d at 603, nevertheless held that a further factual inquiry was needed to ascertain whether some less formal protocol “left the compliance officers with no policy-level discretion,” id. at 603. We now reject the panel’s predictive analysis.
To begin with, the Irving I panel appears to have accepted the plaintiff’s position that, because the 1975 and 1978 inspections were “general inspections,” the compliance officers’ conduct was not discretionary. This conclusion suggests that the panel further assumed that general administrative inspections fall outside the scope of 29 U.S.C. § 657(a) and 29 C.F.R. § 1903.7. See Irving I, 909 F.2d at 603. We cannot accept this construct. As our explication of the statute and regulations demonstrates, see supra Part III(A), general administrative inspections are conducted under the auspices of section 657(a). The relevant regulations, moreover, explicitly grant compliance officers the same broad discretion enjoyed by the Secretary with respect to such inspections. Had the Irving I court not overlooked this important fact, its own logic quite likely would have led it to hold, as we do today, that the discretionary function defense prevails. See Irving I, 909 F.2d at 603 (acknowledging that the statute and regulations, considered alone, appear to confer discretion for covered inspections, but questioning whether they governed the actions of compliance officers).
This error materially altered the decisional calculus. Because the Irving I panel misconstrued the applicability of the regulations to the conduct of compliance officers, it failed properly to consider when a court might' justifiably consult informal policy statements in order to shed light on whether an act is discretionary. Of course, as Irving I suggests, informal agency rules and similar pronouncements may at times bind agency personnel for the purposes of discretionary function exception analysis. See Gaubert, 499 U.S. at 324, 111 S.Ct. 1267. Hence, courts may consult such sources in appropriate cases to determine whether a particular function is (or is not) discretionary. See, e.g., Domme v. United States, 61 F.3d 787, 791 (10th Cir.1995) (applying discretionary function bar when none of the relevant statutes, regulations, or internal agency guidelines specified the “precise manner” in which the Department of Energy was to conduct safety appraisals); Autery v. United States, 992 F.2d 1523, 1529 (11th Cir.1993) (similar, re park inspections). Occasionally, such an informal policy will tip the scales. See McMichael v. United States, 856 F.2d 1026, 1033-34 (8th Cir.1988) (holding that when internal agency guidelines directed government inspectors to follow a detailed regime, discretionary function exception did not apply). Still, recognizing that informal sources sometimes may assist courts in deciding whether a function is discretionary is one thing; synthesizing when and how they may do so is another.
Gaubert itself provides some clues as to when courts ought to consult informal rules. There, the Justices indicated that such rules [165]*165become significant to the discretionary function analysis when an agency promulgates “regulations on some topics, but not on others,” or when it relies on “internal guidelines rather than on published regulations” to govern official conduct. Gaubert, 499 U.S. at 324, 111 S.Ct. 1267. The Court contrasted these situations with those in which agencies announced policy mainly through rulemaMng and/or adjudication. See id. Thus, if an agency establishes policy primarily by promulgating legislative rules, and if those legislative rules unambiguously define the nature of the challenged conduct, the discretionary function inquiry is at an end.
Of course, this formulation requires that the legislative rules be unambiguous and that they define the proper level of conduct. We can well imagine that resort to informal indi-cia may be justified either when an agency’s legislative rules define the conduct of some employees, but not others (e.g., when the regulations define the conduct of a regional official but not of a subordinate whose negligence is alleged to have caused the plaintiffs injury), or when legislative rules create ambiguity (e.g., when the regulations interweave precatory with quasi-mandatory language, as in Kelly v. United States, 924 F.2d 355, 360-61 (1st Cir.1991)). This case, however, involves neither of these circumstances, nor does it involve any other fairly comparable situation. Here, the regulations flow rationally from the enabling statute, directly address the level of conduct at issue, and unambiguously grant OSHA compliance officers discretion over the scope, manner, and details of conducting inspections. Where, as here, the statute and the applicable regulations clearly speak to the nature of the conduct, there is no occasion to consult informal rules.
In this case, moreover, our conclusion would remain unaffected even were we obliged to go beyond formal sources, for, as the regulations adumbrate, OSHA’s informal rules point unerringly in the same direction. At the relevant time, OSHA published (and still publishes) a field operations manual (the Manual), which is a compilation of agency guidelines. These guidelines are intended to limn the agency’s operating procedures. The Manual devotes an entire chapter to describing “General Inspection Procedures.” Discussing the responsibilities of compliance officers, this chapter states in pertinent part:
The conduct of effective inspections requires identification, professional evaluation, and accurate reporting of safety and health conditions and practices. Inspections may vary considerably in scope and detail, depending upon the circumstances of each case.
From that point forward, the chapter essentially mirrors the requirements set forth in the regulations. Importantly, the Manual contains no specific prescription mandating OSHA inspectors to proceed item by item or to cover every nook and cranny of a facility during a general administrative inspection. Consequently, even if it were necessary to consult informal rules in this instance — and we stress that it is not — those rules place the compliance officers’ actions squarely in the maw of the discretionary function exception.10
Of course, the Irving I panel directed the district court to determine OSHA policy by looking beyond the clear statements in the statute, the regulations, and the agency’s internal guidelines. 909 F.2d at 603-05. In the circumstances of this ease, that directive should not have issued. The Gaubeit Court instructed inferior courts to look to the requirements set forth by “established governmental policy” in mounting a discretionary function inquiry. Gaubert, 499 U.S. at 324, 111 S.Ct. 1267 (emphasis supplied).
[166]*166The Court specifically identified only statutes, regulations, and agency guidelines as competent sources for determining government policy. See id. Although we do not suggest that those items invariably will be the exclusive sources for determining established policy, it bears remembering that the Court’s recognition that informal rules may be a relevant source took place against a background understanding, both in administrative law generally and in the OSHA context specifically, that agencies typically make authoritative informal statements of policy positions through published interpretive rules or enforcement guidelines. See Martin v. OSHRC, 499 U.S. 144, 157, 111 S.Ct. 1171, 113 L.Ed.2d 117 (1991). Although anecdotal testimony sometimes may furnish clues regarding the nature of agency policy, it is usually a last-ditch resort. See Kenneth C. Davis & Richard J. Pierce, Jr., 3 Administrative Law Treatise § 17.3, at 108 (3d ed.1994) (placing unwritten rules and “officer’s habit” at the bottom of a list of twelve sources, headed by “legislative rules,” and including interpretative rules, published guidelines, published policy statements, orders, and written but unpublished guidelines, and noting that the power to limit officer discretion decreases “as the reader proceeds down the list”).
The most obvious reason why such sources command less weight is because it matters who speaks. To determine what is agency policy, courts customarily defer to the statements of the official policymaker, not others, even though the others may occupy important agency positions. See Martin, 499 U.S. at 152-53, 111 S.Ct. 1171; see also Director, OWCP v. Eastern Associated Coal Corp., 54 F.3d 141, 147 (3d Cir.1995). This case is a suitable vehicle for application of the principle. Congress has the legal authority to render a function either discretionary or obligatory, and it has delegated that power to the Secretary, not to OSHA’s area directors or compliance officers. Hence, we decline to accord decretory significance to the area director’s or compliance officers’ thoughts on OSHA policy requirements, especially when the plaintiff insists on interpreting this testimony in a manner contrary to both the express statements of Congress and the agency’s institutional pronouncements. Accord Valdez v. United States, 56 F.3d 1177, 1179-180 (9th Cir.1995) (refusing to credit agency employees’ testimony that agency rules were mandatory when plain text of guidelines belied that interpretation; concluding, moreover, that discretionary function exception barred action).
We add a coda. As the Irving I panel itself intimated, 909 F.2d at 604-05, the trial testimony does not unequivocally establish that OSHA imposed on its officers a mandatory duty of inspecting every piece of equipment in a workplace. Rather, the testimony on which the plaintiff relies (and upon which the district court premised its holding) is at best ambiguous — and this erodes any conceivable legitimacy that it otherwise may have had as an expression of agency policy. Thus, even setting aside the statute, regulations, and Manual, we do not believe that any statement in the trial record suffices to support the plaintiffs theory that OSHA had a policy of exhaustively inspecting every machine.11
By way of illustration, consider the following exchange, which is perhaps the plaintiffs best evidence, between her counsel and OSHA’s area director, F. Richard Amirault:
Q. And, by the way, the obligation and procedure of your department is to note and cite specific violations, is it not?
To note — document and — identify and document specific hazards, yes. t>
Machine by machine by machine? <©
As far as we can see. i>
Q. Hazard by hazard by hazard?
A. As can be observed.
[167]*167To begin with, the passage is internally ambiguous in at least one critical way. Given the tenor of Amirault’s answers, it can be construed to mean that inspectors were obligated to note and document every hazard that they saw associated with the machines that they in fact inspected. At no point did Amirault state, directly or by necessary implication, that there was a policy to look at every machine.
Furthermore, even if we interpret this passage favorably to the plaintiff, it is inadequate as a matter of law to support the plaintiffs position. Where, as here, the express statements of Congress and the agency occupy the field, trial testimony by a witness must, if it is to carry any weight, somehow reconcile the witness’s understanding of policy with that authority. At the very least, there must be an indication in the record that the witness demonstrated his awareness of the agency’s formal policy statements, but nevertheless had some other articulable basis that supported his understanding of agency policy.
In the absence of such evidence, the most that is suggested by a passage such as the one quoted above is that the OSHA area director and the compliance officers who inspected the Somersworth Shoe plant subjectively exercised, or intended to exercise, the discretion conferred upon them by law in a particular manner, or, alternatively, that they were unaware of the existence of such discretion. We know from Gaubert that the subjective intent of an agency actor is irrelevant to conducting a discretionary function analysis. See Gaubert, 499 U.S. at 325, 111 S.Ct. 1267. Rather, the focus of the inquiry is on “the nature of the actions taken and on whether they are susceptible to policy analysis.” Id. The OSHA officers’ ambiguous testimony in this case is by itself insufficient to alter the nature of the actions as defined by authoritative formal and informal sources.
There are also passages in the trial record where Amirault refers to OSHA guidelines. This testimony further undermines the plaintiffs theory. For example, when plaintiffs counsel asked Amirault about the Manual, Amirault responded that it was OSHA’s “procedural bible” and, as such, described his staffs “operating procedure.” He unequivocally stated that inspections were conducted pursuant to directions set forth by the Manual:
Q. So that for any general or regular inspection at least they [i.e., the compliance officers] would simply follow the manual and the objective standards of OSHA?
A. Right. Following the manual, the FOM, Field Operations Manual.
This cinches the matter, for, as we have already noted, the Manual provides no support for the plaintiffs theory.
Our conclusion is further confirmed by other statements made by Amirault. Consider, for instance, the following exchange:
Q. And those programmed inspections, as I understand it, would be your random way of just doing spot checks on an entire plant without advance notice?
A. Yes, that’s correct.
Q. And those are the type of inspections that your agency performed on the Somersworth plant in 1975 and 1978?
A. Yes.
Q. We’ve learned through the depositions that those two inspections were what is known as a wall-to-wall inspection, is that correct?
A. I’m going to say yes.
Q. And in such an instance, when one of your safety men goes to a plant, he would spend the whole day or whatever time was necessary to inspect the entire plant for safety hazards.
A. He would be able to walk through, yes.
Read naturally, this passage indicates that general administrative inspections constitute nothing more than “walk throughs” that involve random spot checks. As such, it flatly contradicts the suggestion that the inspectors “could not choose simply to spot cheek certain areas,” Irving I, 909 F.2d at 604, and it places the inspection scheme squarely within the Varig Airlines regime. On any reading, the passage does not come close to establishing that OSHA had a strict policy of requir[168]*168ing inspectors to look in detail at every machine.
C. Policy-Based, Discretion.
Having confirmed the existence of discretion on the compliance officers’ part, what remains is to examine whether that discretion is grounded in policy — a question that none of the prior panels reached. We believe that it is.
The plaintiff contends that the discretionary function defense is doomed because the United States failed to adduce any evidence to support the proposition that OSHA inspectors’ actions are grounded in policy. This argument lacks force. When a function is discretionary, there is a presumption that “the agent’s acts are grounded in policy when exercising that discretion.” Gaubert, 499 U.S. at 324, 111 S.Ct. 1267. Hence, the United States has no burden of production; it may rest, as it did here, on the Gaubert presumption.
The plaintiff next endeavors to overcome the Gaubert presumption by pointing to trial testimony by OSHA employees and noting that they purportedly failed to articulate policy justifications for their actions. But Gaubert requires only that a government agent’s actions be “susceptible” to policy analysis, and insists that courts must disregard analyses that rely on subjective intent to determine whether a discretionary choice is policy-driven. See id. at 325, 111 S.Ct. 1267. Because the plaintiff offers no concrete challenge to the position that OSHA compliance officers’ actions are policy-driven, the Gaubert presumption remains intact.
Even beyond the presumption, we believe that the discretion granted to OSHA inspectors is deeply rooted in policy considerations. The OSH Act’s purpose is to provide for a satisfactory standard of safety, not to guarantee absolute safety. See Industrial Union Dep’t v. American Petroleum Inst., 448 U.S. 607, 646, 100 S.Ct. 2844, 65 L.Ed.2d 1010 (1980) (plurality opinion) (discussing legislative history); Donovan v. General Motors Corp., 764 F.2d 32, 35-36 (1st Cir.1985) (same); cf. Union of Concerned Scientists v. NRC, 824 F.2d 108, 118 (D.C.Cir.1987) (citing Industrial Union and stating, in the context of nuclear regulation, that an “adequate protection” standard “need not, and almost certainly will not” be a level of “zero risk”). A corollary to this observation is that OSHA may legitimately devote its limited enforcement resources to monitoring workplaces and working conditions that pose the most serious threats to worker health and safety. OSHA has done so in part, for example, by adopting inspection priorities12 and an administrative plan to govern programmed general inspections. See, e.g., Industrial Steel Products Co. v. OSHA, 845 F.2d 1330, 1333-34 (5th Cir.1988) (describing OSHA site selection criteria for programmed inspections).
The function of an OSHA compliance officer is an integral part of OSHA’s enforcement policies. When conducting inspections under the auspices of an administrative plan, OSHA compliance officers are expected to study the layout of the facility they are about to investigate, to review its health and safety records, and to interview employer and employee representatives during the inspection about working conditions. One might expect that as a result of such study, OSHA inspectors will make daily judgments about what risks and safety issues most urgently require their attention. At bottom, OSHA inspectors must visit numerous workplaces, all of which present different challenges and issues, and they simply cannot be expected to inspect every item in every plant.13 The day-to-day [169]*169decisions made by compliance officers thus further OSHA’s enforcement policy of ensuring adequate safety in workplaces with a view toward efficient and effective use of limited enforcement resources, and are thus grounded in policy. Cf. Gaubert, 499 U.S. at 331-33, 111 S.Ct. 1267 (explaining that day-to-day decisions of thrift regulators were grounded in policies underlying thrift regulation statutes).
We are not persuaded by the plaintiffs contention that all inspections ought to be painstakingly comprehensive because individual companies rely on OSHA inspections to improve their health and safety conditions. The OSH Act, in no uncertain terms, places primary responsibility for workplace safety on employers, not on the federal government. See 29 U.S.C. § 654(a); Reich v. Simpson, Gumpertz & Heger, Inc., 3 F.3d 1, 4 (1st Cir.1993).
IV. CONCLUSION
This case has disturbing aspects. The government’s inspectors appear to have been negligent and the plaintiff suffered grievous harm. Arrayed in opposition, however, is the core policy that underlies the discretionary function exception: an abiding concern about exposing the government to far-flung liability for action (or inaction) in situations in which it has reserved to its own officials the decision about whether or not to act. Even if the decision may seem wrong in retrospect, or if its implementation is negligent, such decisionmaking by its nature typically requires a balancing of interests (e.g, how to deploy scarce government resources in the accomplishment of worthwhile — but expensive — public needs). Congress reasonably struck this balance by requiring that, ordinarily, liability will not inhere absent an authoritative decision that a specific act should become a governmental responsibility. Under this model, the random and uncodified practices of a local supervisor cannot create the kind of specific obligation that gives rise to liability. Were the law otherwise, there would be scant likelihood of precision or uniformity, and local supervisors would have a perverse incentive to refrain from laying down any rules at all.
We need go no further. Even though exceptions to the FTCA’s waiver of sovereign immunity are construed narrowly, they are not to be ignored. Here, Congress clearly expressed its intent through unequivocal statutory language, and the Secretary of Labor, as Congress’s delegate, adopted legislative rules which faithfully adhere to that monition. The statute and regulations, fairly read, bring the case within the compass of the FTCA’s discretionary function exception, and the agency’s internal guidelines buttress this positioning. Accordingly, we must grant the government the immunity that Congress envisioned. We regret only the plaintiffs unfortunate accident and the added suffering she has endured due to the inordinate delay and erratic decisionmaking that spawned two decades of needlessly protracted litigation.
Reversed. No costs.