Because of a conflict in the decided cases,' we granted certiorari. 454 U. S. 1052 (1981).

II

Since 1919, the ICC has prescribed a uniform bill of lading for use on all interstate domestic shipments of freight by rail. See In re Bills of Lading, 52 I. C. C. 671 (1919), modified, 64 I. C. C. 357 (1921), further modified, 66 I. C. C. 63 (1922). The bill of lading is the basic transportation contract between the shipper-consignor and the carrier; its terms and conditions bind the shipper and all connecting carriers. Texas & Pacific R. Co. v. Leatherwood, 250 U. S. 478, 481 (1919).

'In agreement with the decision of the Fifth Circuit in the present case is Brown Transportation Corp. v. Atcon, Inc., 144 Ga. App. 301, 241 S. E. 2d 15 (1977), cert. denied sub nom. Brown Transport Corp. v. Atcon, Inc., 439 U. S. 1014 (1978) (with two Justices dissenting). The contrary result has been reached in other cases. See, e. g., Consolidated Freightways Corp. v. Pacheco Int'l Corp., 488 F. Supp. 68 (CD Cal. 1979), and Pennsylvania R. Co. v. Marcelletti, 256 Mich. 411, 240 N. W. 4 (1932).

There is disagreement, too, as to whether equitable defenses may be asserted in various other situations where regulated carriers seek to recover lawful tariff charges. Compare, e. g., Aero Mayflower Transit Co. v. Hofberger, 259 Ark. 322, 532 S. W. 2d 759 (1976), and Westover v. United Van Lines, Inc., 154 Ga. App. 865, 270 S. E. 2d 74 (1980) (defenses upheld), with Bartlett-Collins Co. v. Surinam Nav. Co., 381 F. 2d 546 (CA10 1967); American Red Ball Transit Co. v. McCarthy, 114 N. H. 514, 323 A. 2d 897 (1974), cert. denied, 420 U. S. 930 (1975); Western Maryland R. Co. v. Cross, 96 W. Va. 666, 123 S. E. 572 (1924); and Arizona Feeds v. Southern Pacific Transp. Co., 21 Ariz. App. 346, 519 P. 2d 199 (1974) (defenses not recognized).

This division prompted one commentator some years ago to refer to the "striking lack of uniformity in decisions concerning the liability of consignors and consignees despite the obvious need for uniformity in interstate commercial transactions." Note, Carriers: Federal Bills of Lading: Liability of Parties to a Prepaid Shipment, 38 Cornell L. Q. 596, 603 (1953).

"The form of the bill of lading has been modified several times since 1922, see, e. g., In re Bills of Lading, 245 I. C. C. 527 (1941), but only the 1921 and 1922 modifications affected the provisions of the bill of lading relevant to this case.

"Each [term] has in effect the force of a statute, of which all affected must take notice." Ibid. Unless the bill provides to the contrary, the consignor remains primarily liable for the freight charges. When the ICC first promulgated the uniform bill of lading, it stated:

"The consignor, being the one with whom the contract of transportation is made, is originally liable for the carrier's charges and unless he is specifically exempted by the provisions of the bill of lading, or unless the goods are received and transported under such circumstances as to clearly indicate an exemption for him, the carrier is entitled to look to the consignor for his charges." In re Bills of Lading, 52 I. C. C., at 721.

This rule has not changed over time. Recently, the ICC again observed that the consignor's liability "is governed by the bill of lading contract between the parties and must be decided by interpreting that contract." C-G-F Grain Co. v. Atchison, T. & S. F. R. Co., 351 I. C. C. 710, 712 (1976).

Clearly, then, under the contract between Metals as consignor and SP as the carrier, the consignor was primarily liable for the freight charges in question. Just as clearly, however, Metals was in a position to effectuate its release from liability by executing the nonrecourse clause in the bill of lading. Signing that clause would have operated to excuse Metals from liability. By failing to execute the nonrecourse provision, Metals continued to be primarily liable for those charges. Illinois Steel Co. v. Baltimore & O. R. Co., 320 U. S. 508, 513 (1944); New York, N. H. & H. R. Co. v. California Fruit Growers Exchange, 125 Conn. 241, 254-255, 5 A. 2d 353, 359, cert. denied, 308 U. S. 567 (1939). See also Louisville & Nashville R. Co. v. Central Iron Co., 265 U. S. 59, 65-67 (1924).

It is perhaps appropriate to note that a carrier has not only the right but also the duty to recover its proper charges for services performed. Id., at 65-66, and n. 3. See Pitts

burgh, C., C. & St. L. R. Co. v. Fink, 250 U. S. 577, 581-583 (1919). This rule of strict adherence to statutory standards is in line with the historic purpose of the Interstate Commerce Act to achieve uniformity in freight transportation charges, and thereby to eliminate the discrimination and favoritism that had plagued the railroad industry in the late 19th century. Midstate Horticultural Co. v. Pennsylvania R. Co., 320 U. S. 356, 361 (1943); New York, N. H. & H. R. Co. v. ICC, 200 U. S. 361, 391 (1906).

Both the District Court and the Court of Appeals correctly found that SP had established a prima facie case of Metals' liability for the freight charges in question by proving that Metals had failed to sign the nonrecourse clause. This much, indeed, is conceded by Metals. Brief for Respondent 11; Tr. of Oral Arg. 31.

III

SP concedes that its failure to collect all freight charges from Carco before releasing the shipments violated the ICC regulation with regard to at least the first of the three shipments. Id., at 4, 17. See 49 CFR § 1320.1 (1981), quoted in n. 6, supra. The question, then, is whether the Court of Appeals properly found that SP's violation of the regulation provided Metals with an equitable affirmative defense to SP's prima facie case."

A. The ICC has comprehensively regulated the extension of credit to shippers by rail carriers. See 49 CFR pt. 1320 (1981). Yet neither the statute under which the regulations

'Metals now asserts, as well, that SP's actions violated § 7 of the Conditions of the Bill of Lading, see n. 2, supra, and thus constituted a complete abrogation of SP's contractual obligations under the bill of lading. See Brief for Respondent 11. SP answers that this argument was presented to neither the District Court nor the Court of Appeals. See Reply Brief for Petitioner 4. Because the Court of Appeals did not rely on this theory to grant respondent relief, and because we did not grant certiorari to consider this breach-of-contract claim, we decline to address it.

were promulgated, 49 U. S. C. §3(2), nor the regulations themselves intimate that a carrier's violation of the credit rules automatically precludes it from collecting the lawful freight charge. Nor does either contain any words of affirmative defense to a freight charge action. Indeed, to the extent the ICC has spoken to this question, it has stated: "[A] violation of section 3(2) by [a carrier], in itself, would have had no effect on [a consignor's] responsibility for payment of undercharges." C-G-F Grain Co. v. Atchison, T. & S. F. R. Co., 351 I. C. C., at 712. Although § 3(2) "prohibits a rail carrier from delivering freight without collecting all charges thereon[,]... it contains no provision shielding a consignor from liability for lawful charges." Ibid. Thus, at least in dictum, the ICC has suggested that "[t]he question of [a consignor's] liability [under a bill of lading] does not turn on whether any provision of the act has been violated." Ibid.

We view the absence of any provision for an affirmative defense in the ICC's credit regulations as an administrative construction of the statute that aids our determination of congressional intent. "[L]egislative silence is not always the result of a lack of prescience; it may instead betoken permission or, perhaps, considered abstention from regulation. . . . Accordingly, caution must temper judicial creativity in the face of legislative or regulatory silence." Ford Motor Credit Co. v. Milhollin, 444 U. S. 555, 565 (1980). We so regard the administrative silence here. When an administrative agency historically has engaged in comprehensive regulation of an industry's credit practices, the agency's silence regarding an affirmative defense based on a violation of those regulations must be deemed significant.

B. The legislative and administrative history of the credit regulations further indicates that this silence was not inadvertent―the intent of the rules was to protect carriers, not to penalize them. Prior to 1918, the Federal Government did not regulate the extension of credit by rail carriers.

Wartime regulation revealed, however, that a general requirement of payment before delivery would protect the working capital of carriers and avoid discrimination among credit recipients. Cf. Ex parte No. MC-1, 2 M. C. C. 365, 374 (1937). After the first World War, when Congress returned the railroads to private control, § 405 of the Transportation Act, 1920, 41 Stat. 479, added paragraph (2) to §3 of the Interstate Commerce Act. See n. 5, supra. The regulations adopted by the ICC in 1920 under the statute as so amended permitted railroads to extend limited credit to shippers on a nondiscriminatory basis. The regulations have remained largely unchanged to the present time. Until 1971, no court seriously suggested that a violation of the credit regulations precluded a carrier from collecting a freight charge from the party with primary liability. Instead, a defense of estoppel based on a violation of the credit regulations was held to be inconsistent with the purpose of the regulations themselves. Courts were concerned that a rule permitting selective estoppels would defeat the antidiscriminatory purpose of the Act and would weaken the capital structure of common carriers. See, e. g., Western Maryland R. Co. v. Cross, 96 W. Va. 666, 673, 123 S. E. 572, 575 (1924); Chicago Junction R. Co. v. Duluth Log Co., 161 Minn. 466, 469, 202 N. W. 24, 25 (1925); East Texas Motor Freight Lines v. Franklin County Distilling Co., 184 S. W. 2d 505, 507 (Tex. Civ. App. 1944).

Despite the absence of any textual or historical support for an affirmative defense in either the statute or the regulations, the Court of Appeals concluded that Metals could raise SP's failure to comply fully with the regulations as an absolute equitable defense to SP's freight charge action. The Court of Appeals relied primarily on what it regarded as "a closely analogous situation," 641 F. 2d, at 237, presented in Consolidated Freightways Corp. v. Admiral Corp., 442 F. 2d 56 (CA7 1971). On examination, however, that Seventh Circuit case plainly is distinguishable from the present one.