OPINION OF THE COURT
Thе principal issue before us is whether the Occupational Safety and Health Review Commission (OSHRC or the Commission) erred in failing to suppress evidence from an inspection authorized by an ex parte warrant. The contested evidence was the basis of the agency’s decision that Pennsylvania Steel Foundry (Penn Steel) committed numerous violations of the Occupational Safety and Health Act (the Act), 29 U.S.C. § 651 et seq. (1982). An additional issue is whether the Commission improperly enforced a settlement agreement from which Penn Steel contends it withdrew before the agreement was final.
I.
Facts
On June 13, 1977, OSHA compliance inspectors sought to conduct a comprehensive inspection of Penn Steel’s Hamburg, Pennsylvania foundry. Penn Steel refused to permit the inspection without a warrant. On August 15, 1977, OSHA made an ex parte application to a federal magistrate for an inspection warrant. The application set forth that the foundry had been cited in 1973 for three violations, 1 that Penn Steel contested the citation but subsequently withdrew its contest on the ground that the violations had been abated; that after a follow-up inspection in 1974 two more citations were issued, one for a “repeated” violation of the silica dust standards; that ultimately the foundry withdrew its contest to these violations, reprеsenting that the violations had been or would be abated; and that an attorney for Penn Steel advised OSHA by letter dated March 5, 1976 that some abatement controls previously agreed to as to dust levels and noise controls were either economically or technically infeasible. The warrant application also described the National Emphasis Program (NEP) which had been established in 1976 “to reduce hazards in industries reporting a higher than average rate of injuries and illnesses.” App. at 72. The application further stated that iron and steel foundries were among the first target industries selected for inspections, citing foundry illness and injury rates of 26.6 per 100 workers as compared to the national average of 8.8.
On August 25, 1977, the magistrate issued an inspection warrant for Penn Steel’s foundry to be conducted “in accordance with the guidelines set forth in the OSHA National Emphasis Program for Foudries.” App. at 66. The warrant stated that it was ordered pursuant to section 8(a) of the Act, 29 U.S.C. § 657(a), which provides for inspection of the entire workplace “within reasonable limits.” Pursuant to the warrant, OSHA compliance officers conducted a full-scope health and safety inspection of the entire worksite where the foundry is located. OSHA issued citations for 298 violations of OSHA standards.
A hearing оn the citations before an administrative law judge began on January
*1213
15, 1979. After three days, the hearing was recessed to allow the parties to attempt to negotiate a settlement. In August 1979, Penn Steel moved in the Commission for summary judgment on the grounds,
inter alia,
that there was no probable cause for the warrant as required by the Supreme Court’s decision in
Marshall v. Barlow’s, Inc.,
Without reaching the merits of either of these objections, the ALJ expressed the opinion “that the Supreme Court would not apply the exclusionary rule retroactively under circumstances similar to those of this case,” App. at 442, and, after nоting that ex parte warrants had been “standard practice” in OSHA cases prior to Barlow’s, appeared to apply a good faith exception. App. at 443.
The parties settled 240 citations and notified the AU, who recommenced the administrative hearing on December 5, 1979, to hear evidence on the remaining fifty-eight items. On June 27, 1980, the AU issued a preliminary decision and order affirming some items, vacating others and reducing the characterization of still others.
The parties executed a Stipulation of Settlement in June 1981 regarding the 240 settled citations which provided that the “disposition set forth [in the AU’s preliminary decision] shall take effect ... on the date this stipulation becomes a final order of the Commission.” App. аt 80. Both parties reserved their rights under the Act, 29 U.S.C. § 660, to petition for review of the AU’s decision. On July 13, 1981, the AU issued a Final Decision and Order “fully implement[ing]” the preliminary decision on the fifty-eight litigated items, approving the settlement, assessing a $5,000 fine provided in the settlement, and requiring abatement as provided for by the settlement. App. at 77-79.
In its petition for review to the Commission Penn Steel sought suppression of all evidence and dismissal on the probable cause and ex parte warrant grounds raised before the AU. Both Penn Steel and the Secretary contested the AU’s rulings on some of the fifty-eight litigated items. The Commission initially directed review on certain of the litigаted items. There was no action in the case between January 1983 and February 1986. 2
In January 1986, the Commission requested supplemental briefs on several issues, including the applicability of a good faith exception to the exclusionary rule and the effect of this court’s decision in
Cerro Metal Products v. Marshall,
The Commission, by a two-to-one vote, refused to suppress the evidence obtained from the inspection. The Commission treated Penn Steel’s statement of withdrawal from the settlement as a motion to withdraw, which it denied, and held that judgment on the 240 unlitigated items should be entered in accordance with the settlement agreement, which included an assessment of a $5,000 penalty. 3 Penn Steel petitions for review of the Commission’s order.
II.
Existence of a Quorum
As a preliminary matter, Penn Steel argues that no part of the Commission’s decision can be affirmed because there were not two affirmative votes on the existence or absence of probable cause.
The Act provides that “two members of the Commission shall constitute a quorum and official action can be taken *1214 only on the affirmative vote of at least two members.” 29 U.S.C. § 661(f). All three members of the Commission participated in the decision. However, Chairman Buckley declined to take part in the probable cause determination because he believed that the Commission, as an administrative agency within the executive branch, cannot perform functions committed to the judicial branch and hence cannot review a magistrate’s determination of probable cause. The other two Commissioners reached the merits but were divided on probable cause. Penn Steel argues that it was deprived of “its due process right to a decision on each exception presented” because a quorum did not make a finding of probable cause. Petitioner’s Brief at 5.
This court considered a similar argument in
Marshall v. Sun Petroleum Products Co.,
Penn Steel’s couching of its argument in due process terms does not alter the result. In
Sun Petroleum,
we stated: “Like the decision of an equally divided court, the action of an equally divided Commission may be examined by the next link in the hierarchal chain of review.”
III.
Validity of the Warrant
We turn to Penn Steel’s argument that all evidence from the inspection should have been suppressed because the warrant was not supported by an adequate showing of probable cause and was issued ex parte in violation of the agency’s own regulation.
A.
Probable Cause
In
Marshall v. Barlow's, Inc.,
Ordinarily an enforcement program such as that contained in the NEP, which provides for “consultation, training and education, evaluation, and compliance monitoring,” App. at 185, would constitute the type of “general administrative plan” discussed in Barlow’s. Penn Steel argues that this NEP is defective because it does not “regulate[ ] the manner of selection of the premises to be searched.” Petitioner’s Opening Brief at 6-7. It contends that because the NEP provided no explanation of why Penn Steel, in particular, was chosen for an NEP inspection, it cannot serve as the basis for probable cause under Barlow’s.
Penn Steel points to a footnote in
Barlow’s
in which the Court commented that
*1215
“[t]he [OSHA inspection] program was not described ... or any facts presented that would indicate why an inspection of Barlow’s establishment was within the program.”
At least three circuits have upheld inspections pursuant to warrants which were based on the fact that the establishment fell within a particular OSHA enforcement plan. In
In re Establishment Inspection of Gilbert & Bennett Manufacturing Co.,
Thereafter, the Ninth Circuit in
Stoddard Lumber Co. v. Marshall,
Although we recognize that there is contrary authority,
see Brock v. Gretna Machine & Ironworks, Inc.,
*1216 In this case, however, the Secretary does not rely upon the NEP as the sole basis for establishing probable cause. Respondent’s Brief at 47. Apparently OSHA has changed its warrant procedure and therefore the Secretary has little “institutional interest in the court ruling as to whether there was probable cause based on this kind of a warrant application.” Transcript of Argument at 29. Instead, the Secretary argues that there was probable cause for the warrant on the facts set forth in the application particular to Penn Steel in light of its past violations and the letter of its counsel stating that at least some such violations had not been аbated as Penn Steel had agreed to do.
The two Commissioners who reached the probable cause issue both agreed that the earlier violations provided a rational basis for the selection of Penn Steel as an inspection site. Under the particular facts of this case in which the application referred to both Penn Steel’s past violation and the NEP for foundries such as Penn Steel, we agree that the past violations of Penn Steel furnished an ample basis for its selection for early inspection. We therefore reject Penn Steel’s contention that there was no probable cause to support the warrant.
Commissioner Rader, who wrote the dissenting opinion, did so on the basis that Penn Steel’s earlier violations provided probable cause only for a follow-up inspection limited to matters pertaining to noise and dust, but not for the broad NEP inspection that followed. App. at 59. Because we have concluded that the warrant was validly based at least in part on the NEP, which authorizes a broad scope inspection under section 8(a) of the statute, 29 U.S.C. § 657(a), we find inapposite those cases that limit the scope of warrants based on employee complaints under section 8(f) of the Act, 29 U.S.C. § 657(f).
See, e.g., Donovan v. Sarasota Concrete Co.,
B.
Ex Parte Warrant
The second ground on which Penn Steel claims the evidence of violations should be suppressed is the ex parte issuance of the warrant. In
Cerro Metal Products v. Marshall,
Retroactivity of judicial decisions in civil cases is governed by the three factor test enunciated in
Chevron Oil Co. v. Huson,
[T]he decision to be applied nonretroactively must establish a new principle of law, either by overruling clear past precedent on which litigants may have relied, or by deciding an issue of first impression whose resolution was not clearly foreshadowed.
The
Cerro Metal
decision was largely based on the litigation strategy followed by the Secretary in
Barlow’s,
where the Secretary suggested to the Supreme Court that 29 C.F.R. § 1903.4 required adversary process once the employer refused entry.
See Cerro Metal,
The warrant in this case issued seven months after the government’s Statement of Jurisdiction was filed in the Supreme Court in
Barlow’s.
It was this Statement of Jurisdiction which provided part of the basis for our decision in
Cerro Metal
that the government had adopted a litigation strategy in
Barlow’s
“to characterize the regulation as providing for adversary process.”
Cerro Metal,
Thus, under the Chevron test we conclude that we must apply retroactively our holding in Cerro Metal that ex parte warrants were invalid under rules existing at the time the warrant in this case was issued. As a consequence, the ex parte warrant used in this case was invalid.
IY.
Exclusionary Rule
The parties have taken extreme positions on opposing sides of the suppression issue. Penn Steel argues that the inspection pursuant to an ex parte warrant was invalid under the statute and denied it due process and equal protection because other businesses which declined consent were provided with advance notice and the opportunity to object. It claims therefore that all evidence from the inspection should be suppressed.
We have previously declined to express any opinion on the “sharply contested question whether the exclusionary rule applies to OSHA enforcement.”
Babcock and Wilcox Co. v. Marshall,
The Secretary emphasizes the Court’s statement in
Lopez-Mendoza
that “no one would argue that the exclusionary rule should be invoked to prevent an agency from ordering corrective action at a leaking hazardous waste dump if the evidence underlying the order had been improperly obtained____ On the rare occasions that it has considered costs of this type the Court has firmly indicated that the exclusionary rule does not extend this far.”
Id.
at 1046,
The Secretary argues that we should follow the dеcision of the Fifth Circuit in
Smith Steel Casting Co. v. Brock,
We need not, in this case, make the definitive ruling sought by the Secretary on the applicability of the exclusionary rule in all OSHA proceedings. We might be faced with that issue were the evidence the fruit of an unconstitutional warrant or inspection, as in Lopez-Mendoza. Although Penn Steel sеeks to raise the ex parte warrant procedure to the level of a constitutional or statutory violation, it was nothing more than a violation of the Secretary’s own regulation which, in fact, has since been changed to provide for ex parte warrants. See 29 C.F.R. § 1903.4(d) (1986).
The Supreme Court made clear in Barlow’s that there is neither a constitutional nor a statutory impediment to an ex parte warrant. 10 Moreover, we have rejected Penn Steel’s other constitutional objections by holding that the warrant was supported by probable cause and that the search was conducted within the scope of the warrant.
The Supreme Court has made a distinction between application of the exclusionary rule when there has been a constitutional violation and when there has only *1219 been a violation of an agency regulation that is not itself mandated by the Constitution. We believe that distinction governs our decision in this case.
In
United States v. Caceres,
Our reliance on
Caceres
as precedent is supported by the interpretation other circuits have given that opinion. In
United States v. Nuth,
In
Caceres,
the Supreme Court suggested that a court retains discretion in appropriate circumstances to exclude evidence obtained in violation of an agency regulation. Nothing in the circumstances before us convinces us that this is a case in which such exclusion would be appropriate. There would be only marginal deterrent value from applying the exclusionary rule because, as we noted above, the agency’s regulation now provides for ex parte warrants. Also, internal agency rules operate to deter Fourth Amendment violations by agency officials.
11
See Lopez-Mendoza,
On the other hand, the costs of applying the exclusionary rule in this type of case would be substantial. Relevant probative evidence would be lost. Penn Steel was cited for 298 violations of health and safety standards ten years ago. The effect of exclusion would be to require OSHA to begin the inspection procedure all over again to the possible detriment of employees exposed to ongoing workplace hazards on a continuing basis. We conclude that the balance of benefits against social costs requires us to decline to apply the exclusionаry rule when the only procedural defect was obtaining an ex parte warrant *1220 before a regulation permitting its use was promulgated. 12
Y.
Settlement Agreement
Penn Steel’s final contention is that the Commission improperly enforced the settlement agreement on the 240 nonlitigated items. The Commission treated Penn Steel’s statement of withdrawal as a motion to withdraw, and held that although the settlement agreement, both by its terms and Commission precedent, was not final prior to Commission approval, it should be enforced because of the substantial prejudice to the Secretary that would be caused by Penn Steel’s withdrawal and the late date at which Penn Steel chose to withdraw.
We reject the Secretary’s contention that the Settlement Agreement was final when signed.
13
There may be more force in his argument that under this court’s decision in
Marshall v. Sun Petroleum Products Co.,
Penn Steel argues that equity requires that it be allowed to withdraw from a settlement agreement prior to Commission approval because the Secretary is allowed to make such a withdrawal. The Secretary’s authority to withdraw, however, is premised on his special role as the enfоrcer of the Act.
See Sun Petroleum,
Even if the Commission had the power to permit withdrawal from the Settlement Agreement, it retained the discretion to require adherence to the Settlement. It concluded that the equities weigh heavily against allowing Penn Steel to withdraw. The decision that it made cannot be characterized as arbitrary or an abuse of discretion. Allowing Penn Steel to withdraw would impede the Secretary’s use of settlements as a means for enforcing the Aсt in other cases.
VI.
Conclusion
In summary, we have held that the Commission’s action is not invalid for want of a quorum, that the warrant was supported by probable cause and that the scope of the inspection did not exceed that permitted by the warrant, that the ex parte warrant was invalid under our decision in Cerro Metal which is to be applied retroactively, and that the exclusionary rule should not be applied to suppress evidence of violations resulting from a search warrant that was invalid only under a now outdated regulation. We have also held that Penn Steel is *1221 terms of the settlement hound by the agreement on the non-litigated items.
Accordingly, we will deny Penn Steel’s Petition to Review the Commission’s Order dated August 27, 1986.
Notes
. The violations were for exposure of employees to excessive concentrations of silica dust, exposure of an employee to an excessive concentration of iron oxide fume, and exposing employees to toxic materials in a lunch room area. App. at 69.
. No reason for this inaction was given by the parties or by the Commission in its decision.
. The Commission also ruled on the merits of the challenges to the litigated items. These rulings are not at issue in this appeal.
. Although Barlow's was decided after the warrant in this case was issued, none of the parties dispute that the probable cause standard enunciated in Barlow's is the applicable standard.
. We reject Penn Steel’s argument that the inspection exceeded the scope of the warrant because the pattern shop and woodworking machinery in that shop were inspected. The Commission considered Penn Steel’s objection but determined that the definition of the production area to be inspected included the pattern-making shop. We do not find the Commission's decision to be "arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." 5 U.S.C. § 706(2)(A) (1982);
see Donovan v. Adams Steel Erection, Inc.,
. The second and third factors to be considered are whether retrospеctive operation of the rule would further or retard its operation, and whether retrospective application of the rule would work an "injustice or hardship."
. The Commission applied the standards for retroactivity in criminal cases set out in
United States v. Johnson,
. Courts considering whether the exclusionary rule is applicable to OSHA cases prior to the decision in
INS
v.
Lopez-Mendoza,
. Judge Garth would not follow the Fifth Circuit’s decision in
Smith Steel Casting Co. v. Brock,
. The Court stated that it is not “immediately apparent why the advantages of surprise would be lost if, after being refused entry, procedures were available for the Secretary to seek an
ex parte
warrant and to reappear at the premises without further notice to the establishment being inspected.”
Marshall v. Barlow’s, Inc.,
. Such rules include not only the requirement of a warrant issued by a United States magistrate but also a requirement that warrant applications be approved by OSHA Area Directors after consultation with the Regional Solicitor of the Labor Department.
. In light of our decision not to apply the exclusionary rule we do not reach the Secretary’s argument that suppression would be inappropriate under the good faith rule of
United States v. Leon,
. The Commission’s conclusion that the Agreement did not become "final” until approved by it is supported by the language of the Settlement Agreement which states, in part: "the parties request that the stipulation be approved and become a final order of the Commission.” App. at 86. The Agreement specifically reserves the rights of the parties to contest before the Commission the fifty-eight litigated items and states: “The preliminary decision will become effective on the date this stipulation becomes a final order of the Commission.” Id. at 80.
