Mr. Justice BLACK, concurring.
The respondent Minker is a naturalized citizen of the United States. He was subpoenaed by an immigration officer to appear and give testimony as a 'witness.' But Minker was not to be a witness within the traditional meaning of that word, that is, one who testifies in a court proceeding or in a public quasi-judicial hearing of some kind. The immigration officer summoning Minker was not a judge or 'grand jury' of any kind, nor was he at the time acting in any quasi-judicial capacity. Cf. In re Oliver, 333 U.S. 257, 68 S.Ct. 499, 92 L.Ed. 682. He was acting under his broad power as a law enforcement officer to follow up clues and find information that might be useful in later civil or criminal prosecutions brought against persons suspected of violating the immigration and naturalization laws. See, e.g., § 287, Immigration and Nationality Act, 66 Stat. 233, 8 U.S.C. § 1357, 8 U.S.C.A. § 1357; 8 CFR §§ 287.1-287.5. The object in summoning Minker was to interrogate him in the immigration officer's private chambers to try to elicit information 'relating to the possible institution of proceedings seeking the revocation of * * * (Minker's) naturalization. * * *' Information so obtained might be used under some circumstances in court to take away Minker's American citizenship or convict him of perjury or some other crime. Thus the capacity in which this immigration officer was acting was precisely the same as that of a policeman, constable, sheriff, or Federal Bureau of Investigation agent who interrogates a person, perhaps himself a suspect, in connection with murder or some other crime. Apparently Congress has never even attempted to vest FBI agents with such private inquisitorial power. Indeed, this Court has construed congressional enactments as designed to safeguard persons against compulsory questioning by law enforcement officers behind closed doors. McNabb v. United States, 318 U.S. 332, 63 S.Ct. 608, 87 L.Ed. 819; Upshaw v. United States, 335 U.S. 410, 69 S.Ct. 170, 93 L.Ed. 100. And we have frequently set aside state criminal convictions as a denial of due process of law because of coercive questioning of suspects by public prosecutors and other law enforcement officers in their official chambers. See, e.g., Watts v. Indiana, 338 U.S. 49, 69 S.Ct. 1347, 93 L.Ed. 1801; Harris v. South Carolina, 338 U.S. 68, 69 S.Ct. 1354, 93 L.Ed. 1815; Chambers v. Florida, 309 U.S. 227, 60 S.Ct. 472, 84 L.Ed. 716. Yet power of the Attorney General and immigration officers to compel persons, including suspects, to appear and subject themselves to questioning by law enforcement officers in their private chambers is precisely what the Department of Justice claims here. This is no less true because a federal judge must be called on to 'aid' the immigration officer in subjecting a summoned person to questioning. § 235(a), 66 Stat. 198, 8 U.S.C. § 1225(a), 8 U.S.C.A. § 1225(a). For after a court order, as before, the person summoned must go to an immigration officer's private chambers for questioning by him, out of which may come a prosecution against the 'witness' for perjury or some other crime. A purpose to subject aliens, much less citizens, to a police practice so dangerous to individual liberty as this should not be read into an Act of Congress in the absence of a clear and unequivocal congressional mandate. I think the Act relied on here by the Department of Justice should not be so read. I would hold that immigration officers are wholly without statutory authority to summon persons, whether suspects or not, to testify in private as 'witnesses' in denaturalization matters. For this reason I concur in the Court's judgment in this case.
The Department of Justice finds the sweeping power it claims in § 235 of the Immigration and Nationality Act of 1952, 66 Stat. 163, 198, 8 U.S.C. §§ 1101, 1225, 8 U.S.C.A. §§ 1101, 1225. That Act is a comprehensive codification of laws relating to entry, exclusion, domestic control, deportation and naturalization of aliens; the Act also provides the controlling rules and procedures for denaturalizing naturalized citizens. Primary responsibility for administration and enforcement of the Act is vested in the Attorney General, acting chiefly through his subordinates in the Immigration and Naturalization Service. § 103, 66 Stat. 173, 8 U.S.C. § 1103, 8 U.S.C.A. § 1103.