212 F.3d 1301 (D.C. Cir. 2000)
Akzo Nobel Salt, Inc. and Cargill, Incorporated, Petitionersv.Federal Mine Safety and Health Review Commission and Secretary of Labor, Respondents
No. 99-1370
United States Court of AppealsFOR THE DISTRICT OF COLUMBIA CIRCUIT
Argued April 17, 2000Decided May 26, 2000

On Petition for Review of a Final Decision by the Federal Mine Safety and Health Review Commission
Mark N. Savit argued the cause for petitioners.  With him on the brief were Adele L. Abrams, and David J. Farber.
Jerald S. Feingold, Attorney, U.S. Department of Labor, argued the cause for respondent.  With him on the brief was  W. Christian Schumann, Counsel.
Before:  Williams, Randolph and Garland, Circuit Judges.
Opinion for the Court filed by Circuit Judge Williams.
Williams, Circuit Judge:


1
The Federal Mine Safety and  Health Act of 1977 (the "Mine Act") authorizes the Secretary  of Labor, acting through the Mine Safety and Health Administration ("MSHA") to promulgate "mandatoryhealth or safety standards for the protection of life and prevention of  injuries in coal or other mines."  Mine Act S 101(a), 30 U.S.C.  S 811(a).  At issue here is a standard governing escapeways from mines:


2
Every mine shall have two or more separate, properly maintained escape ways to the surface from the lowest levels which are so positioned that damage  to one shall not lessen the effectiveness of the others.  A method of refuge shall be provided while a second opening to the surface is being developed.  A second escape way is recommended, but not required, during the exploration or development of an ore body.


3
30 CFR S 57.11050.


4
When maintenance at Akzo Nobel Salt's Cleveland Mine  required temporary shut-down of one of the mine's two  escape ways, Akzo received a citation for violating this standard.  After successfully contesting the citation before an  ALJ, Akzo lost on the Secretary's appeal to the Federal Mine  Safety and Health Review Commission.  The Commission  took the view--now espoused by the Secretary as well--that  the regulation unambiguously required every mine to have at  least two escapeways operable at all times that miners (other  than ones involved in escapeway repair or maintenance) were  in the mine.  Akzo (together with Cargill, Inc., which purchased the Cleveland Mine during the litigation but will  henceforth be disregarded), petitioned this court for review.


5
The regulation does not have the supposedly unambiguous  meaning assigned it by the Commission (and before us by the  Secretary as well).  "[P]roperly maintained" is not identical  to "continuously functioning."  Moreover, because the Secretary's interpretation of S 57.11050(a) has vacillated over time, we remand for the Commission to ascertain the interpretation  that the Secretary currently espouses and to resolve the case  under standard principles governing deference to an agency's  interpretation of its regulations.


6
The parties have stipulated to the relevant facts.  The Akzo  Cleveland Mine was opened in 1961.  It operates two hoists  to transport miners and material to and from the surface,  each hoist being contained within a separate shaft.  Because  of the construction of the wire ropes used in the hoists, these  ropes must be adjusted periodically to ensure that they're  tight and of equal length.


7
On November 6, 1995 counsel for Akzo wrote to Vernon  Gomez, then MSHA's Administrator for Metal and Nonmetal  Mine Safety and Health, asking for clarification of MSHA's  interpretation of 30 CFR S 57.11050(a) when one escapeway  is taken out of use for repairs, leaving only one escapeway  available for immediate use.  Gomez responded on December  8, 1995, saying that "if a hoist could be returned to service  within 1 hour of the need to be used then evacuation of the  mine would not be required."  On December 15 Akzo's counsel informed the Secretary that it would plan a hoist outage  over the upcoming holidays to test the Gomez interpretation,  which has become known as the "one-hour rule."  On December 25 the planned outage took place.  The hoist was shut  down for roughly three and a half hours;  that period included  a time during which it could not have been returned to  service in less than an hour.  During this shift there were  three miners underground doing work unrelated to the maintenance.  On January 25, 1996 an MSHA inspector issued two  citations under S 104(d) of the Mine Act, 30 U.S.C. S 814(d):one under 30 CFR S 50.10 for failure to report the incident  immediately, and a second one under 30 CFR § 57.11050(a).


8
Akzo contested the January 25th citations (as well as an  earlier citation for failure to comply with S 50.10) pursuant to  S 105(d) of the Mine Act, 30 U.S.C. S 815(d).  Both Akzo and  the Secretary moved for summary decision, and the ALJruled in Akzo's favor, vacating the citations.  The Secretary  did not appeal the decision on S 50.10, so we need not address  it.  As for the S 57.11050(a) citation, the ALJ found that  Gomez's one-hour interpretation was not contained within the  regulation's text and was "a significant departure from  MSHA's apparent prior practice that has a substantial adverse impact on AKZO's mining rights and compliance obligations."  Akzo Nobel Salt, Inc. v. Secretary of Labor, Mine  Safety and Health Administration, 18 F.M.S.H.R.C. 1950,  2027 (ALJ 1996).  It followed that the Gomez letter was "a  substantive rule subject to APA notice, comment, and publication requirements."  Id.  Indeed, the ALJ rejected the contention that the Gomez letter constituted "the prevailing  definitive interpretation[ ] of section 57.11050."  Id. at 2019.  Rather, the letter was "a private communication," which "was  prepared unilaterally and was not shared with other members  of the mining community, and its contents have apparently  never been reduced to other written form."  Id. at 2020.


9
The Secretary appealed, arguing (as summarized by the  Commission) that the one-hour rule was an interpretive rule  and therefore did not require notice-and-comment rulemaking, see 5 U.S.C. S 553(b)(A), and that the interpretation was  "reasonable and consistent with the language and purpose of  the standard."  Secretary of Labor, Mine Safety and Health  Administration v. Akzo Nobel Salt, Inc., 21 F.M.S.H.R.C.  846, 850 (F.M.S.H.R.C. 1999).  In an opinion joined by two  commissioners, the Commission took a more stringent view of  the regulation than Akzo and the ALJ or even the Secretary.It reversed the ALJ on the ground that Akzo's conduct was in  violation of "the plain terms" of the regulation, which it saw  as requiring that "an operator must provide two means of  escape at all times."  Id. at 853.  Commissioner Marks  agreed that the plain meaning of the regulation required  reversal but wrote separately to discuss a variety of matters.Akzo attacks Marks's opinion as "no more than an emotional  screed," Petitioner's Initial Br. at 29, but because the plurality opinion is unsustainable we need not consider the Marks  opinion.


10
We defer to an agency's interpretation of its own regulations "unless it is plainly erroneous or inconsistent with the  regulation," Thomas Jefferson University v. Shalala, 512 U.S.  504, 512 (1994) (internal quotation marks omitted).  And  when, as in this case, the Commission and the Secretary  adopt conflicting interpretations, it is the Secretary's that  deserves deference.  Secretary of Labor, Mine Safety and  Health Administration v. FMSHRC, 111 F.3d 913, 920 (D.C.  Cir. 1997);  see also Martin v. Occupational Safety & Health  Review Comm'n, 499 U.S. 144, 152-53 (1991) (holding that  because the Occupational Safety and Health Act of 1970  invests rulemaking and enforcement authority in the Secretary of Labor, his or her interpretations, rather than those of  the adjudicatory Occupational Safety and Health Review  Commission, are accorded deference).


11
Although at the time this litigation arose the Secretary's  position was the one-hour rule (at least as evidenced by the  Gomez letter and its enforcement action against Akzo), her  primary litigation position here is to ask us to affirm the  Commission on its stated ground--that when miners are  underground, S 57.11050 unambiguously requires, at all  times, two functioning escapeways.  She rests this in part on  the truth that use of the word "shall" indicates that the  condition is mandatory, as well on legislative history.  The  Senate reports both to the Mine Act and to its predecessor  the Coal Act, she argues, contain references to instances  when lives were lost because "a second escapeway was not  provided."  S. Rep. No. 91-411, at 84 (1969) (Coal Act Senate Report);  see also S. Rep. No. 95-181, 95th Cong.2nd Sess. at 4, 1977 U.S. Code Cong. & Admin.Newsp. 3404 (1977) (Mine Act Senate Report).


12
Both the Secretary's textual argument and argument from  legislative history are misplaced to the point of distraction.  The ambiguity in this case is not whether S 57.11050 mandates two escapeways.  It does.  And the Cleveland Mine, unlike those cited in the Senate reports, has two escapeways.  As petitioner rightly observes, a car owner with two cars, one  of them in the shop for an oil change, still "has" two cars.


13
The real issue, as the Secretary quite rightly framed it in  her brief before the Commission, is "what the standard  requires when only one escapeway is functional."  Secretary's  Commission Br. at 8.  Nothing in § 57.11050 definitely addresses this question:  "properly maintained" is not unambiguously the same as "continuously functioning."  Neither the  text, legislative history, nor general safety purpose of the  regulation, nor all three taken together, answer the Secretary's well-framed question unambiguously.  Ultimate resolution of the issue would seem to require some exploration of  the phrase "properly maintained."


14
Had the Secretary projected her view through her various  mouthpieces with any consistency, we would rule on the  permissibility of that view.  But here we have the Gomez  letter's one-hour rule, offered initially by Gomez and pursued  by the Secretary's litigation counsel before the Commission.  Then we have the Secretary's two views before us--the view  that S 57.11050 unambiguously demands immediate evacuation for any period of incomplete functioning, and the view  that immediate evacuation is a reasonable resolution of the  regulation's ambiguity.  The Supreme Court has stated that  when interpreting an ambiguous regulation we normally owe  deference to the Secretary's litigation position before the  Commission.  Martin, 499 U.S. at 157.  The Secretary's  interpretation before the Commission is "agency action, not a  post hoc rationalization of it."  Id.  And, "when embodied in a  citation, the Secretary's interpretation assumes a form expressly provided for by Congress," id. (citing 29 U.S.C. S 658), and is therefore "as much an exercise of delegated  lawmaking powers as is the Secretary's promulgation of" a  regulation.  Id.  But the Secretary now ranks her earlier  view (the Gomez one-hour rule) lowest among her preferences, instead favoring the Commission's "at all times" reading (either as the "plain" message of the regulation or, as a  fallback, as a resolution of its ambiguity).


15
In considering the permissibility of the "at all times"  interpretation, we recognize that courts defer to agency interpretations of ambiguous regulations first put forward in the  course of litigation, but only where they "reflect the agency's  fair and considered judgment on the matter in question."  Auer v. Robbins, 519 U.S. 452, 462 (1997);  Church of Scientology of California v. IRS, 792 F.2d 153, 165 (Silberman, J.,  concurring) (D.C. Cir. 1986);  compare Christensen v. Harris  County, __ U.S. __, 120 S.Ct. 1655, 1662-63, L.Ed.2d  (U.S. 2000) (noting  that agency interpretations that lack the force of law (such  as those embodied in opinion letters and policy statements)  "do not warrant Chevron-style deference" when they interpret ambiguous statutes but do receive deference under  Auer when interpreting ambiguous regulations).  In assessing the likelihood of such "considered judgment," we have  noted, for example, whether the agency had previously  "adopted a different interpretation of the regulation or contradicted its position on appeal," National Wildlife Federation v. Browner, 127 F.3d 1126, 1129 (D.C. Cir. 1997), as, of  course, the Secretary has here.  Compare Association of  Bituminous Contractors, Inc. v. Apfel, 156 F.3d 1246, 1252  (D.C. Cir. 1998), deferring to an agency's litigation position  where it appeared simply to articulate an explanation of  longstanding agency practice.  By contrast, the flip-flops here mark the Secretary'sposition as the sort of "post hoc  rationalizations" to which courts will not defer.  Martin, 499  U.S. at 156.  Moreover, litigation counsel's simultaneous advocacy of several different positions strongly suggests to us  that the Secretary has in fact never grappled with--and thus  never exercised her judgment over--the conundrum posed  by the regulation's clear ambiguity.  We thus do not pass on  the permissibility of any of these interpretations.  On remand, of course, the Secretary might offer a permissible interpretation, yet one which because of concerns over fair  notice could not be applied punitively against Akzo here. Trinity Broadcasting of Florida, Inc. v. FCC, 211 F.3d 618, 630-32 (D.C. Cir. 2000).


16
Accordingly, we vacate the Commission's decision and remand for it to secure from the Secretary an authoritative  interpretation of S 57.11050, and to resolve the case applying  standard deference principles to that interpretation.


17
The decision of the Commission is vacated and remanded.


18
So ordered.

