If the client is a United States citizen, no ground of deportation can be applied.[8]  A person can acquire United States citizenship in several ways:

[8] See Mireles v. Gonzales, 433 F.3d 965 (7th Cir. Jan. 10, 2006) (petition for review of removal order denied over claims that defendant agency failed to establish that respondent is not a citizen of the United States).

Second Circuit

CITIZENSHIP - ACQUIRED CITIZENSHIP - BIOLOGICAL PARENTAGE IS NECESSARY TO A CLAIM TO UNITED STATES CITIZENSHIP UNDER FORMER INA 301(a)(3)
Colaianni v. INS, 490 F.3d 185 (2d Cir. Jun. 15, 2007) (per curiam) (petition for review denied on basis that noncitizen's claim to be United States citizen, advanced as a defense in removal proceedings, was invalid, since biological parentage is necessary for a person to claim citizenship under former INA 301(a)(3) because of the plain language of the statute, which refers to persons "born ... of parents both of whom are citizens of the United States" and pertains only to the acquisition of citizenship "at birth."), citing Marquez-Marquez v. Gonzales, 455 F.3d 548, 556-57 (5th Cir.2006) (rejecting the same argument based upon a plain reading of the statute).

Lower Courts of Second Circuit

CITIZENSHIP - UNCONSTITUTIONAL TO CONVICT OF ILLEGAL REENTRY
Perez v. United States, ___ F.Supp. ___, ___ (D.N.Y. 2006) ("[B]ecause Petitioner has established that he is a United States citizen, it is a constitutional violation to convict him for reentering the United States. As a result, the Court finds that Petitioners conviction and, in turn, his sentence should be vacated pursuant to 28 U.S.C. 2255.")

Fifth Circuit

CITIZENSHIP - BIRTH IN UNITED STATES
Lopez v. Holder, ___ F.3d ___, 2009 WL 682991 (5th Cir. Mar. 17, 2009) (without consent of petitioners, magistrate judge did not have jurisdiction to try citizenship case based on birth).

Other

ILLEGAL REMOVAL OF UNITED STATES CITIZENS
Occasionally, persons are placed in removal proceedings, and even removed, even though they are United States citizens. E.g., Diaz v. Reno, 40 F.Supp. 2d 984 (N.D. Ill.1999) (U.S. citizen who had been ordered summarily excluded from the United States mounts several claims related to summary exclusion after returning to the United States); Fierro v. INS, 66 F. Supp. 2d 229 (D. Mass. 1999) (court enjoins removal of individual pend-ing resolution of claim to United States citizenship).

CITIZENSHIP - FOUNDLINGS
INA 301(f) allows "a person of unknown parentage found in the United States while under the age of five years" to be considered a citizen of the United States unless the person is "shown, prior to his attaining the age of twenty-one years, not to have been born in the United States."

CITIZENSHIP - PROOF OF - CENSUS INFORMATION
United States Citizenship may be sometimes proven by showing a child appeared on a U.S. census in the United States shortly after birth. Contact US Census Bureau. Thanks to Mary Lee Eldridge