In this case of first impression, we are called upon to interpret the meaning of Congress’ 1990 amendment to 10 U.S.C. § 1095 (Supp.1995). Section 1095 allows the military to be reimbursed by insurance carriers for medical expenses it incurs in treating soldiers whom the carriers insure. We determine that the term “no-fault insurance carrier,” as it appears in the statute, is ambiguous. We therefore defer to the interpretation of that term by the agency entitled to administer the statute, the Department of Defense (“DOD”), reverse the summary judgment in favor of the United Services *297Automobile Association (“USAA”), and render summary judgment for the government.1
I.
This case arises from twelve separate automobile accidents2 involving members of the military who were entitled to receive and did receive medical care in a military hospital and who weye also insured by USAA. The service members were treated for their injuries at military hospitals at no cost to the soldiers. 10 U.S.C. §§ 1074, 1076 (Supp. 1995). Each soldier had an individually-owned automobile insurance policy issued by USAA that contained liability coverage, uninsured motorist coverage, coverage for damage to the insured’s vehicle and medical payments coverage (“Medpay”), which covered the insureds for medical costs arising from automobile accidents.
The government filed claims with USAA, seeking reimbursement for costs incurred in treating USAA’s insureds. The government based its claim on 10 U.S.C. § 1095, which provides that “the United States shall have the right to collect from a third-party payer the reasonable costs of health care services incurred by the United States on behalf of such person through a [military hospital]_” Id. at § 1095(a)(1). The statute defines a “third-party payer” as “an entity that provides an insurance, medical service, or health plan by contract or agreement, including an automobile liability insurance or no-fault insurance carrier.” Id. at § 1095(h)(1).
USAA refused to pay, and instead filed a declaratory judgment action against the government, seeking a determination that it did not owe reimbursement. Specifically, USAA sought a determination that it was not a third-party payer under § 1095.
The parties stipulated that there were no disputed facts and filed cross-motions for summary judgment. The district court ruled in USAA’s favor, holding that Medpay is not no-fault insurance and USAA is therefore not a third-party payer liable to the government under § 1095. The government timely appealed.
II.
The government contends that USAA is a “third-party payer” under § 1095, required to reimburse the government for health care the military provides its insureds. We must determine whether USAA is a “third-party payer” because of the inclusion of its Medpay coverage in its automobile policy.
Before 1990, § 1095 defined “third-party payer” as “an entity that provides insurance, medical service or health plan by contract or agreement.” Congress amended the statute in 1990, adding the words “including an automobile liability insurance or no-fault insurance carrier.” The government and USAA have already litigated the issue of whether USAA is a third-party payer because of Med-pay under § 1095 as it was prior to 1990. In United States v. United Services Auto. Ass’n, 5 F.3d 204 (7th Cir.1993), the Seventh Circuit held that USAA was not such a third-party payer.
We are, of course, not bound by the Seventh Circuit’s decision. Principles of estoppel, however, preclude the government from re-litigating against the same party an issue upon which another circuit has ruled against the government. United States v. Stauffer Chem. Co., 464 U.S. 165, 171, 104 S.Ct. 575, 578-79, 78 L.Ed.2d 388 (1984). Thus, if the government is to prevail in its view that USAA is now a third-party payer, it must do so under the 1990 amendments.3 *298We must, therefore, determine whether USAA is an “automobile liability insurance or no-fault insurance carrier.”
We conclude that USAA is a no-fault insurance carrier because Medpay is a form of no-fault insurance. DOD is entrusted to administer § 1095, and it has issued regulations interpreting the term “no-fault insurance” as
an insurance contract providing compensation for health and medical expenses relating to personal injury arising from the operation of a motor vehicle in which the compensation is not premised on who may have been responsible for causing such injury. No-fault insurance includes personal injury protection and medical payments benefits in eases involving personal injuries resulting from operation of a motor vehicle.
32 C.F.R. § 220.12© (1995). USAA urges us to reject this definition, arguing that “no-fault insurance” refers only to a state-adopted regime of automobile insurance that pays without regard to fault.
When an agency has issued an interpretation of a statute it is entitled to administer, our own interpretation of the statute is not entirely de novo. The Supreme Court has given us guidance, in Chevron, U.S.A v. Natural Resources Defense Council, Inc., 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984), in reviewing such agency regulations:
When a court reviews an agency’s construction of the statute which it administers, it is confronted with two questions. First, always, is the question whether Congress has directly spoken to the precise question at issue. If the intent of Congress is clear, that is the end of the matter; for the court, as well as the agency, must give effect to the unambiguously expressed intent of Congress. If, however, the court determines Congress has not directly addressed the precise question at issue, the court does not simply impose its own construction, as would be necessary in the absence of administrative interpretation. Rather, if the statute is silent or ambiguous with respect to the specific issue, the question for the court is whether the agency’s answer is based on a permissible construction of the statute.
Id. at 842-43, 104 S.Ct. at 2781-82 (footnotes omitted).
Accordingly, our first task is to determine whether the statute is ambiguous. If we determine that Congress has directly spoken to the precise issue, then our job is done; we will “give effect to the unambiguously expressed intent of Congress.” Id. at 843, 104 S.Ct. at 2781. If, however, we find that Congress has not plainly spoken to the issue and the statute is ambiguous on its face, we then will determine whether the agency’s construction of the statute is a permissible one.
A statute is ambiguous if it is susceptible to more than one meaning. NORMAN J. SingeR, 2a Sutherland Statutory CONSTRUCTION § 45.02 (5th ed. 1992). In interpreting a statute, we begin with its plain language. Phillips v. Marine Concrete Structures, Inc., 895 F.2d 1033, 1035 (5th Cir.1990). At first glance, either USAA’s or the government’s interpretation of § 1095 seems plausible. Recourse to dictionaries does not clarify the issue, but only serves to prove that the term “no-fault insurance carrier” is ambiguous. One authority defines no-fault as “[o]f or indicating a system of automotive insurance in which accident victims are compensated by their insurance companies without assignment of blame.” Webster’s II New Riverside University Dictionary 797 (1988). This definition supports USAA’s position, as it considers “no-fault” as referring to a system of insurance. Another source supports the government’s view by defining “no-fault” as “of, or relating to, or being a motor vehicle insurance plan under which an accident victim is compensated ... by his own insurance company regardless of who is responsible for the accident.” Webster’s Ninth New Collegiate Dictionary 801 (1989).
Both parties can (and do) claim assistance from a third reference, which defines “no-fault auto insurance” as the
[t]ype of automobile insurance in which claims for personal injury ... are made *299against the claimant’s own insurance company (no matter who was at fault) rather than against the insurer of the party at fault. Under such state ‘no-fault’ statutes only in cases of serious personal injuries and high medical costs may the injured bring an action against the other party or his insurer. No-fault statutes vary from state to state in terms of scope of coverage, threshold amounts, etc.
Blaox’s Law Dictionary 723 (5th ed. 1979). Still another authority defines “no-fault” as “designat[ing] a form of motor vehicle insurance.” Oxford English Dictionary 462 (2d ed. 1989). In its examples of usage, however, it leans toward USAA’s definition. Id. at 462 (“[A] no-fault compensation system in being discussed- [a] strong no-fault insurance bill”). A final source lends credence to the government’s position, defining “no-fault” as “a form of automobile insurance enabling the policyholder in ease of an accident to collect a certain basic compensation ... from his own insurance company without determination of liability.” Random House College Dictionary 902 (1982).
Based on this review of definitions of “no-fault,” we determine that the word is commonly used in both ways, to denote either (1) an insurance policy or (2) a state-imposed insurance system that pays regardless of fault. Thus, the “Battle of the Dictionaries” does not resolve the ambiguity.
Because “no-fault” is an insurance term and can be a term of art, we also consider how the word is used in the insurance field. A leading insurance treatise uses “no-fault” to refer to a state system of insurance without regard to fault. 12A Couoh on Insur-anoe §§ 45:661-678 (2d ed. 1981); see also R. Long, The Law of Liability InsuRanoe § 27.01 at 27-3 (1994). Another treatise, however, refers to insurance policies paying without regard to fault as “nonfault insur-anee.” Robert E. Keeton, Basic Text of INsuranCE Law, § 4.10 at 246 (1971). Therefore, we can see that while “no-fault” is more commonly used in the insurance area to mean a state system paying regardless of fault, it can also be used to refer to a policy that pays regardless of fault.
We therefore conclude that Congress has not “directly addressed the precise question at issue” here.4 Chevron, 467 U.S. at 843, 104 S.Ct. at 2782. It remains for us to determine whether DOD’s construction of that term is a permissible one, and we have no difficulty concluding that it is. DOD’s construction is consistent with the language of the statute, dictionaries, and insurance treatises. It is not, of course, the only permissible construction of the statute, but it is one permissible construction, and that is enough. We are Chevron-bound to conclude that Medpay is a form of no-fault insurance within the meaning of § 1095, and USAA is liable to the government for reimbursement of medical expenses.
The judgment is REVERSED, and summary judgment is RENDERED for the government on the cross-motion for summary judgment.
. The defendants-appellants in this action are William J. Perry, Secretary of Defense, and the United States of America. Both parties will collectively be referred to as the '‘government.”
. It would appear that all of these accidents occurred in states which have retained tort theories as the basis for recovery for injuries in automobile accidents and have not adopted a comprehensive scheme of "no-fault insurance” for dealing with injuries arising out of automobile accidents. It would also appear that these accidents occurred after 1990.
.We take no position as to whether the prior case against USAA was decided correctly. We merely conclude that, because the parties and the issues are the same, the government is precluded from arguing that USAA was a "third-party pay*298er” under the pre-1990 amendments version of the statute.
. The dissent concludes that the statute’s legislative history renders the term "no-fault insurance" unambiguous, although it concedes that the text of the statute is ambiguous. It is a rare case indeed in which legislative history alone will permit us to find that “Congress has ... directly addressed the precise question at issue.” Chevron, 467 U.S. at 843, 104 S.Ct. at 2782. This is not such a case. The dissent acknowledges that the committee reports of the House and Senate merely restate the text of the amendment. See H.Rep. No. 923, 101st Cong., 2d Sess., reprinted at 1990 U.S.C.C.A.N. 3110; H.Rep. No. 665, 101st Cong., 2d Sess., reprinted at 1990 U.S.C.C.A.N. 2931; S.Rep. No. 521, 101st Cong., 2d Sess., U.S.Code Cong. & Admin.News 1990, p. 3283-3.
The "legislative history” relied upon by the dissent is not really legislative history at all, but a general background history of the statute drawn from non-legislative sources. This is an even less reliable basis than legislative history from which to conclude that a statute, ambiguous on its face, is unambiguous in fact. Indeed, we conclude from the general background history of § 1095 that the purpose of the statute is to prevent a windfall to insurers who happen to be liable to members of the armed forces, and that purpose is furthered by DOD's interpretation of the statute. In any event, we respectfully do not believe that the dissent's sources are adequate to allow us to find that "Congress has directly addressed the precise question at issue.”