with whom Mr. Justice Marshall joins, dissenting.
Selective Service Regulation 1625.2, 32 CFR § 1625.2 (1971), relieves a local board of its general obligation to consider a registrant’s claim for deferment whenever the claim is received after the notice to report for induction has been mailed “unless the local board first specifically finds there has been a change in the registrant’s status resulting from circumstances over which the registrant had no control.” The Court of Appeals held that this regulation relieved the local board of the necessity of considering any claim that a registrant’s conscientious objection to war had crystallized after receipt of an induction notice because, in the court’s view, registrants have control over such changes in their beliefs. 422 F. 2d 332 (CA9 1970). The Court here finds it unnecessary to come to grips with this holding and consider whether a conscientious objection claim comes within the terms of this regulation, since it finds the interpretation of the regulation controlled by “a reasonable, consistently applied administrative interpretation.” Ante, at 105.
I cannot defer to an interpretation I cannot discover. All of the cases cited by the Court make clear that judicial interpretation of an ambiguous regulation is to be informed by reference to administrative practice in interpreting and applying a regulation, not by reference to positions taken for the purpose of litigation. See cases cited, ante, at 105. Cf. Citizens to Preserve Overton Park v. Volpe, 401 U. S. 402, 419 (1971). The national Selective Service office has apparently made no national administrative interpretation of the regulation. The only other information presently before us indicates that state Selective Service headquarters in North Carolina and California have interpreted the regulation to require local boards to consider “late crystallization” claims and *120to consider whether the registrant’s conscientious objection was a change occurring after receipt of his induction notice over which he had no control. Brief for Petitioner 28 n. 53. If anything, this suggests that petitioner’s interpretation should prevail. On this state of the record, however, I hardly think administrative practice can properly form the basis of decision.
Moreover, I do not find the regulation to be ambiguous. In the context of a blanket Selective Service regulation applicable to all claims for deferment and exemption, the reference to “circumstances” must be taken to refer to any conditions relevant to eligibility for a deferment or exemption. Since conscientious objection to war is the basis for a deferment, it must constitute a “circumstance” within the plain meaning of the regulation. The question, therefore, is whether that circumstance can be one “over which the registrant had no control.” On that score, I fully agree with the dissent of Judge Merrill below:
“One simply cannot order his conscience to be still or make himself believe what he does not believe and I must reject the implication that it is right and proper that one should suffer loss of status for having failed to bring his conscience to heel.
“Conscientious objection, in truth, is a contradiction of control. Just as a conviction honestly dictated by conscience cannot be banished at the will of the holder, so, conversely, a belief conveniently subject to the control of the holder is not conscientiously entertained.” 422 F. 2d, at 339.
In sum, I think the regulation means that late-crystallization claims asserted prior to induction should be processed by civilian personnel of the local boards, who have been designated by the Congress as the appropriate decisionmakers in these cases, rather than by military personnel during in-service processing. I dissent.