As mentioned last time, the now-outlawed practice of stripping U.S. citizenship from deserters and draft evaders — and the still-current practice of denying them re-entry to the U.S. if they can be convinced to strip themselves of citizenship — goes all the way back to the 1865 “Act to amend the several Acts heretofore passed to provide for the Enrolling and Calling out the National Forces, and for other Purposes”, which in § 21 (13 Stat. 487, 491) provided that:
[I]n addition to the other lawful penalties of the crime of desertion from the military or naval service, all persons who have deserted the military or naval service of the United States, who shall not return to said service, or report themselves to a provost-marshal within sixty days after the proclamation hereinafter mentioned, shall be deemed and taken to have voluntarily relinquished and forfeited their rights of citizenship and their rights to become citizens; and such deserters shall be forever incapable of holding any office of trust or profit under the United States, or of exercising any rights of citizens thereof; and all persons who shall hereafter desert the military or naval service, and all persons who, being duly enrolled, shall depart the jurisdiction of the district in which he is enrolled, or go beyond the limits of the United States, with intent to avoid any draft into the military or naval service, duly ordered, shall be liable to the penalties of this section.
And the President is hereby authorized and required forthwith, on the President to passage of this act, to issue his proclamation setting forth the provisions of this section, in which proclamation the President is requested to notify all deserters returning within sixty days as aforesaid that they shall be pardoned on condition of returning to their regiments and companies or to such other organizations as they may be assigned to, until they shall have served for a period of time equal to their original term of enlistment.
In just one clause, this provided both for stripping of citizenship and prohibition of renaturalisation. These provisions of the Enrollment Act of 1865 were controversial even back when they were introduced, in particular over concerns of due process; I quote the various speeches after the jump.