MR. JUSTICE ROBERTS delivered the opinion of the Court.

The respondent is an alien who entered the United States in 1912 and has since resided here. In 1933 he applied for naturalization to a United States District Court in Arkansas. He made certain admissions to a District Director of Naturalization as a result of which naturalization was withheld and his case was referred to the Department of Labor.

November 25, 1933, the Second Assistant Secretary of Labor issued a warrant for the respondent's apprehension, in which it was recited that he was in the United States in violation of law in that (1) he believes in, advises, advocates or teaches the overthrow, by force or violence, of the Government of the United States; (2) he is a member of, or affiliated with, an organization, association, society, or group that believes in, advises, advocates or teaches the overthrow, by force or violence, of the Government of the United States; (3) he is a member of, or affiliated with, an organization, association, society, or group that writes, circulates, distributes, prints, publishes or displays, or causes to be written, circulated, distributed, printed, published or displayed, or that has in its possession for these purposes written or printed matter advising, advocating or teaching the overthrow, by force or violence, of the Government of the United States; and (4) after his entry into the United States he has been found to have become a member of one of the classes of aliens enumerated in § 1 of the Act of October 16, 1918, as amended by the Act of June 5, 1920, to wit: an alien who is a member of, or affiliated with, an organization, association, society or group that believes in, advises or teaches the overthrow, by force and violence, of the Government of the United States.

The respondent was apprehended and was given hearings before an Immigration Inspector, at which he was represented by counsel and testified in his own behalf. The Government offered in evidence transcripts of his examination by the Naturalization Bureau, of an interview with him by an Immigration Inspector, and his membership book in the Communist Party of the U.S.A., issued November 15, 1932, with stamps affixed showing payment of dues to the end of February, 1933. The rules of the party, set forth in the book, provided that failure to pay dues for three months automatically results in the loss of membership, and it is admitted there is no evidence respondent continued to be a member after March 1, 1933.

The book contained printed matter stating the purposes and objects of the party. The Government also offered a copy of a magazine called "The Communist," dated April 1934, and read into the record excerpts from articles appearing therein. The respondent admitted that he joined the Communist Party in November 1932, asserted that his membership terminated prior to March 1, 1933, and had never been renewed, and professed ignorance of the magazine called "The Communist" and its contents. In some respects his testimony as to his beliefs and actions was contradictory of his statements on prior examinations, and testimony was elicited from him in an effort to show that his denial of present affiliation with the Communist Party might not be made in good faith; but there was no sufficient evidence to sustain that conclusion. After a review of the record by the Board of Review of the Department of Labor, a warrant of deportation was issued by the Assistant Secretary which recites an affirmative finding as to each of the counts in the warrant of arrest and orders the respondent's deportation.

The respondent petitioned a federal district court in Arkansas for a writ of habeas corpus to deliver him from the custody of the Immigration Inspector. The writ was denied. Thereafter he filed the petition in the instant case in the District Court for Louisiana. In this petition he alleged that he had not been accorded a fair hearing; that the Department of Labor had not correctly construed the immigration laws applicable to his case; that the findings were without support in the evidence; that he had been denied due process of law, and that he is not a citizen of Poland, to which the warrant directed his remission. The District Court dismissed the writ. The respondent appealed to the Circuit Court of Appeals assigning error to the District Court's action in denying each of his contentions. That court found that the hearings had been fair, but held that each of the findings recited in the warrant was without support in the evidence. The court was of opinion the evidence failed to show that the respondent is now a member of the Communist Party or that he or that party, in 1933, taught, advocated, or incited the overthrow of the Government by force and violence, and that the record was bare of evidence to countervail his denial that he had ever taught or believed in the unlawful destruction or overthrow of the Government by force. The court held that the Acts of 1918 and 1920 were passed to meet a situation caused by crises in Russia in 1918 and 1919; that the major changes in policy and conduct of the Soviet Socialist Republics which had taken place between 1918 and 1933 rebutted the implications arising from membership in the Communist Party at the time the Acts were adopted; that mere membership in that party in 1933 is not a statutory ground for deportation. The order of the District Court was reversed and the cause was remanded for further proceedings not inconsistent with the opinion.

The Government moved for a rehearing, pressing specially the contention that the overwhelming weight of authority is to the effect that membership in the Communist Party is sufficient to warrant deportation. The petition was entertained, the judgment was amended to provide: "Reversed, with directions to try the issues de novo as suggested in Ex Parte Fierstein, 41 F.2d p. 54"; and a rehearing was denied. Judge Sibley dissented on the ground that on the basis of the respondent's membership book which refers to the Third Communist Internationale, the court could take judicial notice of the objectives and programs of the Communist Party and the Third Internationale.

The United States petitioned for certiorari, asserting that the single question presented is "whether the court below erred in failing to sustain an order of deportation against respondent, an alien who in 1932 became a member of the Communist Party of the United States." In its specification of errors to be urged the Government enumerated (1) the holding that an alien who became a member of the party in 1932 is not, by reason of that fact, subject to deportation; (2) the holding that the evidence before the Secretary of Labor concerning the principles of the party was insufficient to sustain the order; (3) the remand for a trial de novo in the District Court, and (4) the failure to affirm the judgment of the District Court. As reason for the granting of the writ the Government urged a conflict of decision on the question whether membership by an alien in the Communist Party of America subjects him to deportation. By reason of the allegation of conflict and the action of the Circuit Court of Appeals in ordering a trial de novo in the District Court, we granted the writ.

The Government does not attempt to support the warrant of deportation on the second and third grounds therein specified, namely, that the respondent "is a member of or affiliated with" an organization described in the Act. The only evidence of record is that his membership ceased months before the issue of the warrant for his arrest. The contention is that respondent is deportable because, after entry, he became a member of a class of aliens described in § 1 of the Act, to wit, a member of the Communist Party, an organization membership in which is made a cause of deportation because the organization believes in, advocates, and teaches the overthrow of the Government of the United States by force and violence. This contention presents the question whether the Act renders former membership in such an organization, which has ceased, a ground of deportation. Respondent insists that the statute makes only present membership in an organization described in the Act such ground.

Section 1 of the Act of October 16, 1918, as amended in 1920, has to do with the exclusion of alien immigrants and specifies five classes, members of which may not be admitted to the United States. One of these classes — subsection (c) — includes "aliens who believe in, advise, advocate, or teach, or who are members of or affiliated with any organization, association, society, or group, that believes in, advises, advocates, or teaches . . . the overthrow by force or violence of the Government of the United States. . . ."

Section 2 of the Act of 1918, which was not altered by the Act of 1920, deals with deportation. It provides that "any alien who, at any time after entering the United States, is found to have been at the time of entry, or to have become thereafter, a member of any of the classes of aliens enumerated" in § 1, shall, upon warrant of the Secretary of Labor, be taken into custody and deported, in the manner provided by law.

Relying on the phrases italicized in the quotation, the Government insists that the section embraces an alien who, after entry, has become a member of an organization, membership in which, at the time of his entry, would have warranted his exclusion, although he has ceased to be a member at the time of his arrest. We hold that the Act does not provide for the deportation of such an alien. This conclusion rests not alone upon the language, but, as well, upon the context and the history of the legislation.

The phrase "at any time" qualifies the verb "found." Thus, if at any time the Secretary finds that at entry the alien was a member, or has thereafter become and is a member, he may be deported. The natural meaning is that, as the alien was excludable for present membership, he is deportable for present membership subsequently acquired. The Government's construction, which collocates the phrase "at any time" with the phrase "or to have become thereafter" is unnatural and strained. If Congress meant that past membership, of no matter how short duration or how far in the past, was to be a cause of present deportation the purpose could have been clearly stated. The section does not bear this import.

By the first section of the Act, as amended in 1920, aliens are to be excluded who are members of a described organization. The section does not require the exclusion of those who have been in the past, but are no longer, members. When the Congress came to provide for deportation, instead of again enumerating and defining the various classes of aliens who might be deported, it provided that if at any time it should be found that an alien had been admitted and, at the time of admission, was a member of any of the proscribed classes, or had thereafter become such, he should be deported. It is not to be supposed that past membership, which does not bar admission, was intended to be a cause of deportation. And the fact that naturalization is denied to an alien only on the ground that he " is a member of or affiliated with any organization entertaining" disbelief in or opposition to organized government, and not for past membership or affiliation, lends added force to this view.

In the absence of a clear and definite expression, we are not at liberty to conclude that Congress intended that any alien, no matter how long a resident of this country, or however well disposed toward our Government, must be deported, if at any time in the past, no matter when, or under what circumstances, or for what time, he was a member of the described organization. In the absence of such expression we conclude that it is the present membership, or present affiliation — a fact to be determined on evidence — which bars admission, bars naturalization, and requires deportation. Since the statute deals not only with membership in an organization of the described class, but with affiliation therewith and, as well, with belief and teaching, it enables the Secretary of Labor, as trier of the facts, fully to investigate and to find the true relation, belief and activity of the alien under investigation.

The legislative history of the statute supports this conclusion. By Act of March 3, 1903, Congress directed the exclusion of "anarchists, or persons who believe in or advocate the overthrow by force or violence of the Government of the United States, . . ." and also of any "person who disbelieves in or who is opposed to all organized government, or who is a member of or affiliated with any organization entertaining and teaching such disbelief in or opposition to all organized government . . ." The only section authorizing deportation of such persons is directed to an alien found to have entered in violation of the Act, if proceeded against within three years after entry. These provisions were reenacted without alteration in the Act of February 20, 1907.

The first legislation authorizing deportation of persons who had entered lawfully is H.R. 6060, enacted by the 63rd Congress but vetoed by President Wilson January 28, 1915. This bill required deportation of "any alien who within five years after entry shall be found advocating or teaching" the defined doctrines. It also altered existing law in respect of deportation of those who had entered illegally to provide that " at any time within five years after entry, any alien who at the time of entry was a member of one or more of the classes excluded by law" should be deported.

A bill, in substance the same, was introduced in the 64th Congress and enacted February 5, 1917, over Presidential veto. While this measure was in course of passage, the Chairman of the House Committee in charge of it moved, on behalf of the Committee, to amend § 19 by inserting the phrase "at any time" so that the section should provide for deportation of "any alien who at any time after entry shall be found advocating or teaching" forcible overthrow of the government. The Act, as adopted, was in this form. The purpose of the amendment was to make plain that no time limit was fixed for deportation of aliens found advocating the doctrine. The Act of 1917 was amended by that of October 16, 1918, here under consideration, which, by its title, purported to apply to "aliens who are members of the anarchistic and similar classes. . . ."

Section 1 enlarged one of the classes of excludable aliens by the addition of the words "aliens who are members of or affiliated with any organization that entertains a belief in, teaches or advocates the overthrow by force or violence of the Government of the United States. . . ." Section 2 modified the earlier Act in respect of deportation, both in form and substance. The provision for deportation of those who, at the time of entry, were members of one of the proscribed classes was retained, but the five year period of limitation within which deportation might be had was eliminated. The provision for deportation of aliens of anarchistic and similar classes was expanded by including as causes of deportation all the causes of exclusion enumerated in § 1 which were themselves much broader than those included in the 1917 Act. Thus, although there was no provision in the Act of 1917 for deportation of aliens who did not personally advocate the proscribed doctrine, but were members of an organization which did, the Act of 1918 embodied such a provision. This alteration, and the elimination of the five year time limitation, were the important changes, relevant to the question under examination, which the Act of 1918 effected in the earlier legislation. These modifications lend no support to the contention that § 2 of the Act of 1918 was intended to make quondam membership a ground of deportation.

Nor is there anything in the formal alteration worked by the Act of 1918 which leads to a different conclusion. Section 19 of the Act of 1917 dealt in distinct clauses with the various classes of aliens who might be deported, specifying in one clause an alien "who at the time of entry was a member of the classes excluded by law" and, in another clause, an alien "who, at any time after entry, shall be found advocating or teaching" the obnoxious doctrines. Section 2 of the Act of 1918 combined the clauses dealing with the two groups in a single sentence, with a somewhat different locution. We think this consolidation was not intended to alter the substantive law as it theretofore stood.

The only decisions which support the Government's position are those in the Second Circuit. We cannot approve their reasoning or result. It is claimed that the administrative construction has always accorded with the Government's contention in the present case. We cannot find that there has been such a uniform construction as requires an interpretation of the Act in accordance with that view. The administrative construction seems to have been in favor of the respondent's view until after the decision in the Yokinen case, and the construction seems to have been changed in deference to the decision in that case.

Our reading of the statute makes it unnecessary to pass upon the conflicting contentions of the parties concerning the adequacy of the evidence before the Secretary concerning the purposes and aims of the Communist Party or the propriety of the court's taking judicial notice thereof.

The Solicitor General suggests that the evidence is sufficient to sustain the warrant of deportation on the first ground therein stated, namely, that the respondent believes in and teaches the overthrow, by force and violence, of the Government of the United States. It is said that the error of the Circuit Court of Appeals in reversing the District Court is, in this aspect, so plain that we should notice it, although the petition does not present the question. We have the power to do this in the case of plain error, but we exercise it only in clear cases and in exceptional circumstances.

We do not know on what grounds the District Judge's action rested since he wrote no opinion. The Circuit Court of Appeals held the evidence insufficient to support the Secretary's finding. We think that the record does not justify a reversal of the holding of the court below upon this point.

The Circuit Court of Appeals remanded the cause to the District Court for a trial de novo. In this we think there was error. The proceeding for deportation is administrative. If the hearing was fair, if there was evidence to support the finding of the Secretary, and if no error of law was committed, the ruling of the Department must stand and cannot be corrected in judicial proceedings. If, on the other hand, one of the elements mentioned is lacking, the proceeding is void and must be set aside. A district court cannot upon habeas corpus, proceed de novo, for the function of investigation and finding has not been conferred upon it but upon the Secretary of Labor. Only in the event an alleged alien asserts his United States citizenship in the hearing before the Department, and supports his claim by substantial evidence, is he entitled to a trial de novo of that issue in the district court. The status of the relator must be judicially determined, because jurisdiction in the executive to order deportation exists only if the person arrested is an alien; and no statutory proceeding is provided in which he can raise the question whether the executive action is in excess of the jurisdiction conferred upon the Secretary.

It follows from what has been said that, as the Secretary erred in the construction of the statute, the writ must be granted and the respondent discharged from custody.

The judgment of the Circuit Court of Appeals is accordingly modified and the cause is remanded to the District Court with instructions to proceed in conformity with this opinion.

Affirmed with modification.