Justice Marshall
delivered the opinion of the Court.
Section 340 (a) of the Immigration and Nationality Act of 1952, 66 Stat. 260, as amended, 8 U. S. C. § 1451 (a), requires revocation of United States citizenship that was “illegally procured or . . . procured by concealment of a material fact or by willful misrepresentation.”1 The Government brought this denaturalization action, alleging that petitioner procured his citizenship illegally or by willfully misrepresenting a material fact. The District Court entered judgment for petitioner, but the Court of Appeals reversed and ordered entry of a judgment of denaturalization. We granted certiorari, 444 U. S. 1070, to resolve two questions: whether petitioner’s failure to disclose, in his application for a visa to come to this country, that he had served during the Second World War as an armed guard at the Nazi concentration camp at Treblinka, Poland, rendered his citizenship revocable as “illegally procured” or procured by willful misrepresentation of a material fact, and if so, whether the District Court nonetheless possessed equitable discretion to refrain from entering judgment in favor of the Government under these circumstances.
[494]*494I
A
Petitioner was born in the Ukraine in 1907. He was drafted into the Russian Army in June 1941, but was captured by the Germans shortly thereafter. After being held in a series of prisoner-of-war camps, petitioner was selected to go to the German camp at Travnicki in Poland, where he received training as a concentration camp guard. In September 1942, he was assigned to the Nazi concentration camp at Treblinka in Poland, where he was issued a uniform and rifle and where he served as a guard during 1942 and 1943. The infamous Treblinka concentration camp was described by the District Court as a “human abattoir” at which several hundred thousand Jewish civilians were murdered.2 After an armed uprising by the inmates at Treblinka led to the closure of the camp in August 1943, petitioner was transferred to a German labor camp at Danzig and then to the German prisoner-of-war camp at Poelitz, where he continued to serve as an armed guard. Petitioner was eventually transferred to Hamburg where he served as a warehouse guard. Shortly before the British forces entered that city in 1945, petitioner discarded his uniform and was able to pass as a civilian. For the next four years, he worked in Germany as a laborer.
[495]*495B
In 1948, Congress enacted the Displaced Persons Act (DPA or Act), 62 Stat. 1009, to enable European refugees driven from their homelands by the war to emigrate to the United States without regard to traditional immigration quotas. The Act’s definition of “displaced persons” 3 eligible for immigration to this country specifically excluded individuals who had “assisted the enemy in persecuting civil [ians]” or had “voluntarily assisted the enemy forces ... in their operations . ...” 4 Section 10 of the DPA, 62 Stat. 1013, placed the burden of proving eligibility under the Act on the person seeking admission and provided that “[a]ny person who shall willfully make a misrepresentation for the purpose of gaining admission into the United States as an eligible displaced person shall thereafter not be admissible into the United States.” The Act established an elaborate system for determining eligibility for displaced person status. Each applicant was first interviewed by representatives of the International Refugee Organization of the United Nations (IRO) who ascertained that the person was a refugee or displaced person.5 The ap[496]*496plicant was then interviewed by an official of the Displaced Persons Commission,6 who made a preliminary determination about his eligibility under the DPA. The final decision was made by one of several State Department vice consuls, who were specially trained for the task and sent to Europe to administer the Act.7 Thereafter, the application was reviewed by officials of the Immigration and Naturalization Service (INS) to make sure that the applicant was admissible into the United States under the standard immigration laws.
In October 1949, petitioner applied for admission to the United States as a displaced person. Petitioner falsified his visa application by lying about his wartime activities. He told the investigators from the Displaced Persons Commission that he had been a farmer in Sarny, Poland, from 1937 until March 1942, and that he had then been deported to Germany and forced to work in a factory in Poelitz until the end of the war, when he fled to Hamburg.8 Petitioner told the same [497]*497story to the vice consul who reviewed his case and he signed a sworn statement containing these false representations as part of his application for a DPA visa. Petitioner’s false statements were not discovered at the time and he was issued a DPA visa, and sailed to the United States where he was admitted for permanent residence. He took up residence in Connecticut and for three decades led an uneventful and law-abiding life as a factory worker.
In 1969, petitioner applied for naturalization at the INS office in Hartford, Conn. Petitioner did not disclose his wartime service as a concentration camp armed guard in his application,9 and he did not mention it in his sworn testimony to INS naturalization examiners. The INS examiners took petitioner’s visa papers at face value and recommended that his citizenship application be granted. On this recommendation, the Superior Court of New Haven County granted his petition for naturalization and he became an American citizen on April 23,1970.
C
Seven years later, after petitioner had moved to Miami Beach and become a resident of Florida,10 the Government filed this action in the United States District Court for the Southern District of Florida to revoke petitioner’s citizenship. The complaint alleged that petitioner should have been deemed ineligible for a DPA visa because he had served as an armed guard at Treblinka and had committed crimes or atroc[498]*498ities against inmates of the camp because they were Jewish. The Government charged that petitioner had willfully concealed this information both in applying for a DPA visa and in applying for citizenship, and that therefore petitioner had procured his naturalization illegally or by willfully misrepresenting material facts.11
The Government’s witnesses at trial included six survivors of Treblinka who claimed that they had seen petitioner commit specific acts of violence against inmates of the camp.12 Each witness made a pretrial identification of petitioner from a photo array that included his 1949 visa photograph, and three of the witnesses made courtroom identifications. The Government also called as a witness Kempton Jenkins, a career foreign service officer who served in Germany after the war as one of the vice consuls who administered the DPA. Jenkins had been trained to administer the Act and had re[499]*499viewed some 5,000 visa applications during his tour of duty. Record 711-714, 720-722. Without objection from petitioner, Jenkins was proffered by the Government and accepted by the court, as an expert witness on the interpretation and application of the DPA. Id., at 719-721, 726-727, 734.
Jenkins testified that the vice consuls made the final decision about an applicant’s eligibility for displaced person status.13 He indicated that if there had been any suggestion that an applicant “had served or been involved in” a concentration camp, processing of his application would have been suspended to permit a thorough investigation. Id., at 766. If it were then determined that the applicant had been an armed guard at the camp, he would have been found ineligible for a visa as a matter of law. Id., at 767-768, 822. Jenkins explained that service as an armed guard at a concentration camp brought the applicant under the statutory exclusion of persons who “assisted the enemy in persecuting civil [ians],” regardless of whether the applicant had not volunteered for service14 or had not committed atrocities against inmates. Id., at 768, 797-798. Jenkins emphasized that this interpretation of the Act was “uniformly” accepted by the vice consuls, and that furthermore, he knew of no case in which a known concentration camp guard was found eligible for a DPA visa.15 Id., at 767. Jenkins also described the elabo[500]*500rate system that was used to screen visa applicants and he testified that in interviewing applicants, the vice consuls bent over backwards in interrogating each person to make sure the applicant understood what he was doing. Id., at 746.
Petitioner took the stand in his own behalf. He admitted his service as an armed guard at Treblinka and that he had known that thousands of Jewish inmates were being murdered there. Id., at 1442, 1461-1452, 1465. Petitioner claimed that he was forced to serve as a guard and denied any personal involvement in the atrocities committed at the camp, id., at 1276, 1297-1298, 1539-1540; he insisted that he had merely been a perimeter guard. Petitioner admitted, however, that he had followed orders and shot in the general direction of escaping inmates during the August 1943 uprising that led to closure of the camp. Id., at 1507-1509, 1546, 1564. Petitioner maintained that he was a prisoner of war at Treblinka, id., at 1495, although he admitted that the Russian armed guards significantly outnumbered the German soldiers at the camp,16 that he was paid a stipend and received a good service stripe from the Germans, and that he was allowed to leave the camp regularly but never tried to escape. Id., at 1467-1471, 1489-1494, 1497, 1508.17 Finally, petitioner conceded that he deliberately gave false statements about his wartime activities to the investigators from the Displaced Persons Commission and to the vice consul who reviewed his visa application. Id., at 1518-1524.
The District Court entered judgment in favor of petitioner. [501]*501455 F. Supp. 893 (1978). The court found that petitioner had served as an armed guard at Treblinka and that he lied about his wartime activities when he applied for a DPA visa in 1949.18 The court, found, however, that petitioner was forced to serve as a guard. The court concluded that it could credit neither the Treblinka survivors’ identification of petitioner nor their testimony,19 and it held that the Government had not met its burden of proving that petitioner committed war crimes or atrocities at Treblinka.
Turning to the question whether petitioner’s false statements about his activities during the war were misrepresentations of “material” facts, the District Court, relying on our decision in Chaunt v. United States, 364 U. S. 350 (1960), held that the Government had to prove
“that either (1) facts were suppressed ‘which, if known, would have warranted denial of citizenship’ or (2) that their disclosure ‘might have been useful in an investiga[502]*502tion possibly leading to the discovery of other facts warranting denial of citizenship.’ ” 455 F. Supp., at 915 (quoting 364 U. S., at 355).
The District Court rejected the Government’s claim that disclosure of petitioner’s service as a concentration camp armed guard would have been grounds for denial of citizenship. The court therefore ruled that the withheld facts were not material under the first Chaunt test. The Government argued, however, that the second Chaunt test did not require proof that the concealed facts prevented an investigation that would have revealed facts warranting denial of citizenship. The Government contended instead that the second test merely required proof that an investigation might have uncovered such facts and it argued that petitioner’s concealment of his service at Treblinka fell within this test. The District Court conceded that the language of Chaunt was ambiguous enough to support the Government’s interpretation of the second test. But relying on decisions-by the United States Courts of Appeals for the Third and Ninth Circuits,20 the District Court rejected the Government’s position and interpreted both Chaunt tests as requiring proof that “the true facts would have warranted denial of citizenship.” 455 F. Supp., at 916. Applying this test, the court ruled that petitioner’s false statements were not “material” within the meaning of the denaturalization statute. In doing so, the court first rejected Jenkins’ testimony and held that petitioner was not ineligible for a DPA visa. The court concluded that petitioner did not come under the DPA’s exclusion of persons who had assisted in the persecution of civilians because he had served involuntarily. Second, the court found that although disclosure of petitioner’s service as a Treblinka guard “certainly would” have prompted an investigation into [503]*503his activities, the Government had failed to prove that such an inquiry would have uncovered any additional facts warranting denial of petitioner’s application for a visa.. Id., at 916.21
As an alternative basis for its decision, the District Court held that even assuming that petitioner had misrepresented “material” facts, equitable and mitigating circumstances required that petitioner be permitted to retain his citizenship. Specifically, the court relied on its finding that the evidence that petitioner had committed any war crimes or atrocities at Treblinka was inconclusive, as well as the uncontroverted evidence that he had been responsible and law-abiding since coming to the United States. The District Court suggested that this Court had not previously considered the question whether a district court has discretion to consider the equities in a denaturalization ' case. The court reasoned that since naturalization courts have considered the equities in determining whether citizenship should be granted, similar discretion should also be available in denaturalization proceedings.
The Court of Appeals for the Fifth Circuit reversed and remanded the case with instructions to enter judgment for the Government and to cancel petitioner’s certificate of citizenship. 597 F. 2d 946 (1979). Although the Court of Appeals agreed with the District Court that Chaunt was controlling on the question of the materiality of petitioner’s false statements, it disagreed with the District Court’s interpreta[504]*504tion of the second Chaunt test as requiring proof of ultimate facts warranting denial of citizenship. Instead, the Court of Appeals agreed with the Government that the second Chaunt test requires only clear and convincing proof that (a) disclosure of the true facts would have led to an investigation and (b) the investigation might have uncovered other facts warranting denial of citizenship.22
In applying its formulation of the second Chaunt test to the facts of the case, the Court of Appeals concluded that one part of the test was satisfied by the District Court’s finding that the American authorities would have conducted an investigation if petitioner had disclosed that he had served as an armed guard at Treblinka. The Court of Appeals then found that Jenkins’ testimony and other evidence before the District Court clearly and convincingly proved that the investigation might have resulted in denial of petitioner’s application for a visa 23 and the Court of Appeals held that petitioner procured his naturalization “by misrepresentation and concealment of his whereabouts during the war years and his service as a concentration camp guard.” 597 F. 2d, at 953. The Court of Appeals further held that the District Court had erred in supposing that it had discretion to enter judgment in favor of petitioner notwithstanding a finding that [505]*505petitioner had procured his naturalization by willfully concealing material facts. The Court of Appeals concluded that “[t]he denaturalization statute . . . does not accord the district courts any authority to excuse the fraudulent procurement of citizenship.” Id., at 954. Accordingly, the Court of Appeals held that petitioner’s citizenship must be revoked.24 We affirm, but for reasons which differ from those stated by the Court of Appeals.
II
Our examination of the questions presented by this case must proceed within the framework established by two lines of prior decisions of this Court that may, at first blush, appear to point in different directions.
On the one hand, our decisions have recognized that the right to acquire American citizenship is a precious one, and that once citizenship has been acquired, its loss can have severe and unsettling consequences. See Costello v. United States, 365 U. S. 265, 269 (1961); Chaunt v. United States, 364 U. S., at 353; Baumgartner v. United States, 322 U. S. 665, 675-676 (1944); Schneiderman v. United States, 320 U. S. 118, 122 (1943). For these reasons, we have held that the Government “carries a heavy burden of proof in a proceeding to divest a naturalized citizen of his citizenship.” Costello v. United States, supra, at 269. The evidence justifying revocation of citizenship must be “ 'clear, unequivocal, and convincing’ ” and not leave “ 'the issue in doubt.’ ” Schneiderman v. United States, supra, at 125 (quoting Maxwell Land-Grant Case, 121 U. S. 325, 381 (1887)). Any less exacting standard would be inconsistent with the importance of the right that [506]*506is at stake in a denaturalization proceeding. And in reviewing denaturalization cases, we have carefully examined the record ourselves. See, e. g., Costello v. United States, supra; Chaunt v. United States, supra; Nowak v. United States, 356 U. S. 660 (1958); Baumgartner v. United States, supra.
At the same time, our cases have also recognized that there must be strict compliance with all the congressionally imposed prerequisites to the acquisition of citizenship. Failure to comply with any of these conditions renders the cértificate of citizenship “illegally procured,” and naturalization that is unlawfully procured can be set aside. 8 U. S. C. § 1451 (a); Afroyim v. Rusk, 387 U. S. 253, 267, n. 23 (1967). See Maney v. United States, 278 U. S. 17 (1928); United States v. Ness, 245 U. S. 319 (1917); United States v. Ginsberg, 243 U. S. 472 (1917). As we explained in one of these prior decisions:
“An alien who seeks political rights as a member of this Nation can rightfully obtain them only upon terms and conditions specified by Congress. . . .
“No alien has the slightest right to naturalization unless all statutory requirements are complied with; and every certificate of citizenship must be treated as granted upon condition that the government may challenge it . . . and demand its cancellation unless issued in accordance with such requirements.” United States v. Ginsberg, supra, at 474-475.
This judicial insistence on strict compliance with the statutory conditions precedent to naturalization is simply an acknowledgment of the fact that Congress alone has the constitutional authority to prescribe rules for naturalization,25 and the courts’ task is to assure compliance with the particular prerequisites to the acquisition of United States citizen[507]*507ship by naturalization legislated to safeguard the integrity of this “priceless treasure.” Johnson v. Eisentrager, 339 U. S. 763, 791 (1950) (Black, J., dissenting).
Thus, what may at first glance appear to be two inconsistent lines of cases actually reflect our consistent recognition of the importance of the issues that are at stake — for the citizen as well as the Government — in a denaturalization proceeding. With this in mind, we turn to petitioner’s contention that the Court of Appeals erred in reversing the judgment of the District Court.
Ill
Petitioner does not and, indeed, cannot challenge the Government’s contention that he willfully misrepresented facts about his wartime activities when he applied for a DPA visa in 1949. Petitioner admitted at trial that he “willingly” gave false information in connection with his application for a DPA visa so as to avoid the possibility of repatriation to the Soviet Union.26 Record 1520. The District Court specifically noted that there was no dispute that petitioner “lied” in his application. 455 F. Supp., at 914. Thus, petitioner falls within the plain language of the DPA’s admonition that “[a]ny person who shall willfully make a misrepresentation for the purposes of gaining admission into the United States as an eligible displaced person shall thereafter not be admissible into the United States.” 62 Stat. 1013. This does not, however, end our inquiry, because we agree with the Government 27 that this provision only applies to willful misrepresentations about “material” facts.28 The first issue we must [508]*508examine then, is whether petitioner’s false statements about his activities during the war, particularly the concealment of his Treblinka service, were "material.”
At the outset, we must determine the proper standard to be applied in judging whether petitioner’s false statements were material. Both petitioner and the Government have assumed, as did the District Court and the Court of Appeals, that materiality under the above-quoted provision of the DP A is governed by the standard announced in Chaunt v. United States, 364 U. S. 350 (1960). But we do not find it so obvious that the Chaunt test is applicable here. In that case, the Government charged that Chaunt had procured his citizenship by concealing and misrepresenting his record of arrests in the United States in his application for citizenship, and that the arrest record was a “material” fact within the meaning of the denaturalization statute.29 Thus, the materiality standard announced in that case pertained to false statements in applications for citizenship, and the arrests that Chaunt failed to disclose all took place after he came to this country. The case presented no question concerning the lawfulness of his initial entry into the United States.
In the instant case, however, the events on which the Government relies in seeking to revoke petitioner’s citizenship took place before he came to this country and the Govern[509]*509ment is seeking to revoke petitioner’s citizenship because of the alleged unlawfulness of his initial entry into the United States. Although the complaint charged that petitioner misrepresented facts about his wartime activities in both his application for a visa and his application for naturalization, both the District Court and the Court of Appeals focused on the false statements in petitioner’s application for a visa. Thus, under the analysis of both the District Court and the Court of Appeals, the misrepresentation that raises the ma-terality issue in this case was contained in petitioner’s application for a visa.30 These distinctions plainly raise the important question whether the Chaunt test for materiality of misrepresentations in applications for citizenship also applies to false statements in visa applications.
It is, of course, clear that the materiality of a false statement in a visa application must be measured in terms of its effect on the applicant’s admissibility into this country. See United States v. Rossi, 299 F. 2d 650, 652 (CA9 1962). At the very least, a misrepresentation must be considered material if disclosure of the true facts would have made the applicant ineligible for a visa. Because we conclude that disclosure of the true facts about petitioner’s service as an armed guard at Treblinka would, as a matter of law, have made him ineligible for a visa under the DP A, we find it unnecessary to resolve the question whether Chaunt’s materiality test also governs false statements in visa applications.
Section 2 (b) of the DPA, 62 Stat. 1009, by incorporating the definition of “[p]ersons who will not be [considered dis[510]*510placed persons]” contained in the Constitution of the IR.O, see n. 3, supra, specifically provided that individuals who “assisted the enemy in persecuting civil [ians]” were ineligible for visas under the Act.31 Jenkins testified that petitioner’s service as an armed guard at a concentration camp — whether voluntary or not — made him ineligible for a visa under this provision.32 Jenkins’ testimony was based on his firsthand [511]*511experience as a vice consul in Germany after the war reviewing DPA visa applications. Jenkins also testified that the practice of the vice consuls was to circulate among the other vice consuls the case files of any visa applicant who was shown to have been a concentration camp armed guard. Record 826. Thus, Jenkins and the other vice consuls were particularly well informed about the practice concerning the eligibility of former camp guards for DPA visas. The District Court evidently agreed that a literal interpretation of the statute would confirm the accuracy of Jenkins’ testimony. 455 F. Supp., at 913. But by construing § 2 (a) as only excluding individuals who voluntarily assisted in the persecution of civilians, the District Court was able to ignore Jenkins’ uncontroverted testimony about how the Act was interpreted by the officials who administered it.33
[512]*512The Court of Appeals evidently accepted the District Court’s construction of the Act since it agreed that the Government had failed to show that petitioner was ineligible for a DP A visa. 597 F. 2d, at 953. Because we are unable to find any basis for an “involuntary assistance” exception in the language of § 2 (a), we conclude that the District Court’s construction of the Act was incorrect. The plain language of the Act mandates precisely the literal interpretation that the District Court rejected: an individual’s service as a concentration camp armed guard — whether voluntary or involuntary- — made him ineligible for a visa. That Congress was perfectly capable of adopting a “voluntariness” limitation where it felt that one was necessary is plain from comparing § 2 (a) with § 2 (b), which excludes only those individuals who “voluntarily assisted the enemy forces ... in their operations . . . .” Under traditional principles of statutory construction, the deliberate omission of the word “voluntary” from § 2 (a) compels the conclusion that the statute made all those who assisted in the persecution of civilians ineligible for visas.34 See National Railroad Passenger Corp. [513]*513v. National Assn, of Railroad Passengers, 414 U. S. 453, 458 (1974); Botany Worsted Mills v. United States, 278 U. S. 282, 289 (1929). As this Court has previously stated: “We are not at liberty to imply a condition which is opposed to the explicit terms of the statute. ... To [so] hold ... is not to construe the Act but to amend it.” Detroit Trust Co. v. The Thomas Barium, 293 U. S. 21, 38 (1934). See FTC v. Sun Oil Co., 371 U. S. 505, 514-515 (1963). Thus, the plain language of the statute and Jenkins’ uncontradicted and unequivocal testimony leave no room for doubt that if petitioner had disclosed the fact that he had been an armed guard at Treblinka, he would have been found ineligible for a visa under the DPA.35 This being so, we must conclude that peti[514]*514tioner’s false statements about his wartime activities were “willfu[l] [and material] misrepresentation [s] [made] for the purpose of gaining admission into the United States as an eligible displaced person.” 62 Stat. 1013. Under the express terms of the statute, petitioner was “thereafter not . . . admissible into the United States.” Ibid.
Our conclusion that petitioner was, as a matter of law, ineligible for a visa under the DPA makes the resolution of this case fairly straightforward. As noted, supra, at 506-507, our cases have established that a naturalized citizen’s failure to comply with the statutory prerequisites for naturalization renders his certificate of citizenship revocable as “illegally procured” under 8 U. S. C. § 1451 (a). In 1970, when petitioner filed his application for and was admitted to citizenship, §§ 316 (a) and 318 of the Immigration and Nationality Act of 1952, 8 U. S. C. §§ 1427 (a) and 1429, required an applicant for citizenship to be lawfully admitted to the United States for permanent residence.36 Lawful admission for per[515]*515manent residence in turn required that the individual possess a valid unexpired immigrant visa. At the time of petitioner’s initial entry into this country, § 13 (a) of the Immigration and Nationality Act of 1924, ch. 190, 43 Stat. 153, 161 (repealed in 1952), provided that “[n]o immigrant shall be admitted to the United States unless he (1) has an unexpired immigration visa . . . .”37 The courts at that time consistently held that § 13 (a) required a valid visa and that a visa obtained through a material misrepresentation was not valid. See, e. g., Ablett v. Brownell, 99 U. S. App. D. C. 387, 391, 240 F. 2d 625, 629 (1957); United States ex rel. Jankowski v. Shaughnessy, 186 F. 2d 580, 582 (CA2 1951). Section 10 of the DP A, 62 Stat. 1013, provided that “all immigration laws, . . . shall be applicable to . . . eligible displaced . . . persons who apply to be or who are admitted into the United States pursuant to this Act.” And as previously noted, petitioner was inadmissible into this country under the express terms of the DPA. Accordingly, inasmuch as petitioner failed to satisfy a statutory requirement which Congress has imposed as a prerequisite to the acquisition of citizenship by naturalization, we must agree with the Government that petitioner’s citizenship must be revoked because it was “illegally procured.” See Polites v. United States, 364 U. S. 426, 436-437 (1960); Schwinn v. United States, 311 U. S. 616 (1940); Money v. United States, 278 U. S., at 22-23; United States v. Ginsberg, 243 U. S., at 475; Luria v. United States, 231 U. S. 9, 17 (1913); Johannessen v. United States, 225 U. S. 227, 240 (1912). Cf. Schneiderman v. United States, 320 U. S., at 163 (Douglas, J., concurring).38 In the lexicon [516]*516of our cases, one of the “jurisdictional facts upon which the grant [of citizenship] is predicated,” Johannessen v. United States, supra, at 240, was missing at the time petitioner became a citizen.
B
This conclusion would lead us to affirm on statutory grounds (and not on the basis of our decision in Chaunt), the judgment of the Court of Appeals. Petitioner argues, however, that in a denaturalization proceeding, a district court has discretion to consider the equities in determining whether citizenship should be revoked. This is the view adopted by the District Court but rejected by the Court of Appeals. It is true, as petitioner notes, that this Cburt has held that a denaturalization action is a suit in equity. Knauer v. United States, 328 U. S. 654, 671 (1946); Luria v. United States, supra, at 27-28. Petitioner further points to numerous cases in which the courts have exercised discretion in determining whether citizenship should be granted. See, e. g., In re Iwanenko’s Petition, 145 F. Supp. 838 (ND Ill. 1956); Petition of R., 56 F. Supp. 969 (Mass. 1944). Petitioner would therefore have us conclude that similar discretion should be available to a denaturalization court to weigh the equities in light of all the circumstances in order to arrive at a solution that is just and fair. He then argues that if such power exists, the facts of this case, particularly his record of good conduct over the past 29 years and the reasonable doubts about some of the allegations in the Government’s complaint, all weigh in favor of permitting him to retain his citizenship. Although petitioner presents this argument with respect to revocation of citizenship procured through willful misrepresentation of material facts, we assume that petitioner believes that courts should also be allowed to weigh the equities in [517]*517deciding whether to revoke citizenship that was “illegally procured,” which is our holding in this case.
We agree with the Court, of Appeals that district courts lack equitable discretion to refrain from entering a judgment of denaturalization against a naturalized citizen whose citizenship was procured illegally or by willful misrepresentation of material facts. Petitioner is correct in noting that courts necessarily and properly exercise discretion in characterizing certain facts while determining whether an applicant for citizenship meets some of the requirements for naturalization.39 But that limited discretion does not include the authority to excuse illegal or fraudulent procurement of citizenship. As the Court of Appeals stated: “Once it has been determined that a person does not qualify for citizenship, . . . the district court has no discretion to ignore the defect and grant citizenship.” 597 F. 2d, at 954. By the same token, once a district court determines that the Government has met its burden of proving that a naturalized citizen obtained his citizenship illegally or by willful misrepresentation, it has no discretion to excuse the conduct. Indeed, contrary to the District Court's suggestion, see supra, at 503, this issue had been settled by prior decisions of this Court. In case after case, we have rejected lower court efforts to moderate or otherwise avoid the statutory mandate of Congress in denaturalization proceedings. For example, in United States v. Ness, 245 U. S. 319 (1917), we ordered the denaturalization of an individual who “possessed the personal qualifications which entitle aliens to admission and to citizenship,” id., at 321, but who had failed to file a certificate of arrival as required by statute. We explained that there was “no power . . . vested in the naturalization court to dispense with” this requirement. [518]*518Id., at 324. We repeat here what we said in one of these earlier cases:
“An alien who seeks, political rights as a member of this Nation can rightfully obtain them only upon the terms and conditions specified by Congress. Courts are without authority to sanction changes or modifications; their duty is rigidly to enforce the legislative will in respect of a matter so vital to the public welfare. United States v. Ginsberg, 243 U. S., at 474-475.
See Maney v. United States, 278 U. S., at 22-23; Johannessen v. United States, 225 U. S., at 241-242.
In sum, we hold that petitioner’s citizenship must be revoked under 8 U. S. C. § 1451 (a) because it was illegally procured. Accordingly, the judgment of the Court of Appeals is affirmed.40
So ordered.
The Chief Justice concurs in the judgment.