delivered the opinion of the Court.
Appellee was indicted under § 242 (d) of the Immigration and Nationality Act of 1952, 66 Stat. 163, 208, originally part of § 23 of the Internal Security Act of 1950, 64 Stat. 1010, on the charge that, as an alien against whom a final order of deportation had been outstanding *195for more than six months, he had wilfully failed to give information to the Immigration and Naturalization Service as required by that section. Appellee moved to dismiss the indictment on the grounds, inter alia, that it failed to state an offense within the statute and in the alternative, if it did so, that the statute was unconstitutional. The District Court held that the statute as construed by it was not unconstitutional. 140 F. Supp. 815. Thereupon the United States filed a motion for clarification of the court’s opinion, and appellee filed a supplemental motion to dismiss the indictment, claiming that the statute as construed by the district judge did not authorize the Government to elicit the demanded information. The District Court, in a second opinion, dismissed the indictment for failure to state an offense. 140 F. Supp., at 820. The case was brought here, 352 U. S. 817, under the Criminal Appeals Act of 1907, as amended, 18 U. S. C. § 3731.
The Section, as amended, 68 Stat. 1232, 8 U. S. C. (Supp. II) § 1252 (d), is as follows:
“(d) Any alien, against whom a final order of deportation as defined in subsection (c) heretofore or hereafter issued has been outstanding for more than six months, shall, pending eventual deportation, be subject to supervision under regulations prescribed by the Attorney General. Such regulations shall include provisions which will require any alien subject to supervision (1) to appear from time to time before an immigration officer for identification; (2) to submit, if necessary, to medical and psychiatric examination at the expense of the United States; (3) to give information under oath as to his nationality, circumstances, habits, associations, and activities, and such other information, whether or not related to the foregoing, as the Attorney General may deem fit and proper; and (4) to conform to such *196reasonable written restrictions on his conduct or activities as are prescribed by the Attorney General in his case. Any alien who shall willfully fail to comply with such regulations, or willfully fail to appear or to give information or submit to medical or psychiatric examination if required, or knowingly give false information in relation to the requirements of such regulations, or knowingly violate a reasonable restriction imposed upon his conduct or activity, shall be fined not more than $1,000 or imprisoned not more than one year, or both.”
The District Court construed § 242 (d) as conferring upon the Attorney General “power to supervise the alien to make sure he is available for deportation, and no further power.” Accordingly, it held that clause (3) of this subsection is to be restricted to require only “such information as is necessary to enable the Attorney General to be certain that the alien is holding himself in readiness to answer the call to be deported when it comes.” 140 F. Supp., at 819-820. The court found that the questions listed in the indictment, which are set forth in the margin,* were not relevant to appellee’s availability for depor*197tation. The interpretation that the District Court thus placed on § 242 (d) was derived from a consideration of its relation to the entire statutory scheme of deportation of which it is a part. The court below was further guided by the principle that requires courts, when construing statutes, to avoid constitutional doubts. “To hold that the statute intended to give an official the unlimited right to *198subject a man to criminal penalties for failure to answer absolutely any question the official may decide to ask would raise very serious constitutional questions.” Id., at 821.
The Government does not support the questions put to the alien on the basis of the construction that the District Court placed upon § 242 (d). This construction authorizes all questions reasonably appropriate to keep the Attorney General advised regarding the continued availability for departure of a deportable alien. The Government contends that the District Court misconceived the scope of the statute. It points to what it characterizes as “the eloquent breadth” of clause (3), whereby the alien is to give “such other information, whether or not related to the foregoing, as the Attorney General may deem fit and proper.” This, says the Government, establishes a requirement “in the broadest possible statutory terms for the furnishing of information by the alien.” And this view, it maintains, fits into the statutory scheme. In the circumstances defined by § 242 (a), an alien may be detained pending determination of deportability; and § 242 (c) authorizes such detention for six months after the alien has been found deportable. So, the Government argues, § 242 (d), though it does not authorize detention after six months, is an attempt to accomplish in a modified form the ends that would justify detention in the earlier stages of the deportation process. Our decision in Carlson v. London, 342 U. S. 524, is heavily invoked. If, so the argument runs, detention of active alien Communists pending deportation hearings was sustainable under § 242 (a), the national interest in avoiding recurrence of past Communist activity for which appellee is being deported should at least require him to answer questions regarding any present Communist relationships. For this view of the purpose of supervision, support is found in two other statutory provisions: *199§ 242 (e), making an alien’s wilful failure to leave the country a felony but providing for suspension of sentence and release of the alien upon judicial consideration, inter alia, of the effect of release upon the national security and the likelihood of resumption of conduct that serves as a basis for deportation; and the recital in § 2 (13) of the Internal Security Act of 1950, that “numerous aliens who have been found to be deportable, many of whom are in the subversive, criminal, or immoral classes . . . are free to roam the country at will without supervision or control.” 64 Stat. 987.
The language of § 242 (d)(3), if read in isolation and literally, appears to confer upon the Attorney General unbounded authority to require whatever information he deems desirable of aliens whose deportation has not been effected within six months after it has been commanded. The Government itself shrinks from standing on the breadth of these words. But once the tyranny of literalness is rejected, all relevant considerations for giving a rational content to the words become operative. A restrictive meaning for what appear to be plain words may be indicated by the Act as a whole, by the persuasive gloss of legislative history or by the rule of constitutional adjudication, relied on by the District Court, that such a restrictive meaning must be given if a broader meaning would generate constitutional doubts.
The preoccupation of the entire subsection of which clause (3) is a part is certainly with availability for deportation. Clause (1) requires the alien’s periodic appearance for the purpose of identification, and clause (2) dealing with medical and psychiatric examination, when necessary, clearly is directed to the same end; and the “reasonable written restrictions on [the alien’s] conduct or activities” authorized by clause (4) have an implied scope to be gathered from the subject matter, i. e., the object of the statute as a whole. Moreover, this limi*200tation of “reasonableness” imposed by clause (4) upon the Attorney General’s power to restrict suggests that, if we are to harmonize the various provisions of the section, the same limitation must also be read into the Attorney General’s seemingly limitless power to question under clause (3). For, assuredly, Congress did not authorize that official to elicit information that could not serve as a basis for confining an alien’s activities. Nowhere in § 242 (d) is there any suggestion of a power of broad supervision like unto that over a probationer. When Congress did want to deal with the far-flung interest of national security or the general undesirable conduct of aliens, it gave clear indication of this purpose, as in § 242 (e). In providing for the release of aliens convicted of wilful failure to depart, that subsection specifically requires courts to inquire into both the effect of the alien’s release upon national security and the likelihood of his continued undesirable conduct.
The legislative history likewise counsels confinement of the mere words to the general purpose of the legislative scheme of which clause (d) is a part, namely, the actual deportation of certain undesirable classes of aliens. Section 242 (d), as it was reported by the House Judiciary Committee and passed by the House in 1949, was in its present state in all but one significant respect. It provided for indefinite detention of any alien who wilfully failed to comply with the regulations, to appear, to give information or to submit to medical examination, or who knowingly gave false information or violated a reasonable restriction upon his activity. H. R. Rep. No. 1192, 81st Cong., 1st Sess., pp. 2-3. The report of the House Committee, although in several places focusing only upon availability for deportation, does indicate concern over the threat to the national interest represented by undesirable but undeportable aliens. The Senate Judiciary Committee, while sharing the desire of the House *201to control the activities of such aliens, substituted for the House bill's detention provision the imposition of criminal penalties for failure to comply with the conditions of supervision. The report of the Senate Committee significantly states the reason for the change: “This provision in the bill as it passed the House of Representatives appears to present a constitutional question.” S. Rep. No. 2239, 81st Cong., 2d Sess., p. 8. This history, although suggesting a desire to exercise continuing control over the activities as well as the availability of aliens whose deportation had been ordered but not effected, shows a strong congressional unwillingness to enact legislation that may subject the Attorney General’s supervisory powers to constitutional challenge.
Acceptance of the interpretation of § 242 (d) urged by the Government would raise doubts as to the statute’s validity. By construing the Act to confer power on the Attorney General and his agents to inquire into matters that go beyond assuring an alien’s availability for deportation we would, at the very least, open up the question of the extent to which an administrative officer may inhibit deportable aliens from renewing activities that subjected them to deportation. See 70 Harv. L. Rev. 718. This is not Carlson v. Landon, supra, where the question was whether an alien could be detained during the customarily brief period pending determination of deportability. Contrariwise, and as the Senate and House Committees recognized in passing on § 242 (d), supervision of the undeportable alien may be a lifetime problem. In these circumstances, issues touching liberties that the Constitution safeguards, even for an alien “person,” would fairly be raised on the Government’s view of the statute.
The path of constitutional concern in this situation is clear.
“When the validity of an act of the Congress is drawn in question, and even if a serious doubt of *202constitutionality is raised, it is a cardinal principle that this Court will first ascertain whether a construction of the statute is fairly possible by which the question may be avoided.” Crowell v. Benson, 285 U. S. 22, 62.
See also cases cited in the concurring opinion of Mr. Justice Brandeis in Ashwander v. Tennessee Valley Authority, 297 U. S. 288, 348, note 8.
Section 242 (d) is part of a legislative scheme designed to govern and to expedite the deportation of undesirable aliens, and clause (3) must be placed in the context of that scheme. As the District Court held and as our own examination of the Act confirms, it is a permissible and therefore an appropriate construction to limit the statute to authorizing all questions reasonably calculated to keep the Attorney General advised regarding the continued availability for departure of aliens whose deportation is overdue. Accordingly, the judgment of the District °°urt is
Affirmed.
Mr. Justice Whittaker took no part in the consideration or decision of this case.“(a) Q. Do you subscribe to the Daily Worker?
“ (b) Q. Mr. Witkovich, can you read in any other language other than Slovene and English?
“(c) Q. Since the order of supervision was entered on March 4, 1954, have you at any time visited the office of the ‘Narodny Glasnik/ 1413 West 18th Street, Chicago, Illinois?
“(d) Q. Since the order of supervision was entered on March 4, 1954, Mr. Witkovich, have you ever visited the offices of the Bohemian publication ‘Nova Dova’ or the Slovakian publication 'Ludovy Noviny/ 1510 West 18th Street, Chicago, Illinois?
“(e) Q. Do you know the editor of the ‘Narodni Glasnik’?
“(f) Q. Do you know Leo Fisher?
“(g) Q. Do you know Anton Minerich?
“(h) Q. Do you know Nick Rajkovich?
*197“(i) Q. Do you know Arsenio Bartl?
“(j) Q. Do you know John Zuskar?
“(k) Q. Do you know Calvin Brook?
“(1) Q. Since the order of deportation was entered in your case on June 25, 1953 have you attended any meeting of the Communist Party of the U. S. A.?
“(m) Q. Since the order of supervision was entered on March 4, 1954 have you attended any meeting of any organization other than the singing club?
“(n) Q. Have you addressed any lodges of the Slovene National Benefit Society requesting their aid in your ease, since the order of deportation was entered June 25, 1953?
“(o) Q. Have you distributed petitions or leaflets published by the Slovene National Benefit Society seeking aid for you, in your behalf, in your deportation ease since the order of deportation was entered June 25, 1953?
“(p) Q. Since the order of supervision have you attended any meetings or lectures at the Peoples Auditorium, 2457 West Chicago Avenue, Chicago, Illinois?
“(q) Q- Since the order of supervision was entered against you have you attended any meetings or socials at the Chopin Cultural Center, 1547 North Leavitt Street, Chicago?
“(r) Q. Have you attended any movies since your order of supervision was entered at the Cinema Annex, 3210 West Madison Street, Chicago ?
“(s) Q. Are you acquainted with an individual named Irving Franklin ?
“(t) Q. Are you now a member of the Communist Party of U. S. A.?
“(u) Q. Are you now or have you ever been a member of the Slovene American National Council?
“(v) Q. Are you now or have you ever been a member of the United Committee of South Slavic Americans?”