Whenever there is a declared war between the United States and any foreign nation or government, or any invasion or predatory incursion is perpetrated, attempted, or threatened against the territory of the United States by any foreign nation or government, and the President makes public proclamation of the event, all natives, citizens, denizens, or subjects of the hostile nation or government, being of the age of fourteen years and upward, who shall be within the United States and not actually naturalized, shall be liable to be apprehended, restrained, secured, and removed as alien enemies. The President is authorized in any such event, by his proclamation thereof, or other public act, to direct the conduct to be observed on the part of the United States, toward the aliens who become so liable; the manner and degree of the restraint to which they shall be subject and in what cases, and upon what security their residence shall be permitted, and to provide for the removal of those who, not being permitted to reside within the United States, refuse or neglect to depart therefrom; and to establish any other regulations which are found necessary in the premises and for the public safety.

When an alien who becomes liable as an enemy, in the manner prescribed in section 21 of this title, is not chargeable with actual hostility, or other crime against the public safety, he shall be allowed, for the recovery, disposal, and removal of his goods and effects, and for his departure, the full time which is or shall be stipulated by any treaty then in force between the United States and the hostile nation or government of which he is a native citizen, denizen, or subject; and where no such treaty exists, or is in force, the President may ascertain and declare such reasonable time as may be consistent with the public safety, and according to the dictates of humanity and national hospitality.

After any such proclamation has been made, the several courts of the United States, having criminal jurisdiction, and the several justices and judges of the courts of the United States, are authorized and it shall be their duty, upon complaint against any alien enemy resident and at large within such jurisdiction or district, to the danger of the public peace or safety, and contrary to the tenor or intent of such proclamation, or other regulations which the President may have established, to cause such alien to be duly apprehended and conveyed before such court, judge, or justice; and after a full examination and hearing on such complaint, and sufficient cause appearing, to order such alien to be removed out of the territory of the United States, or to give sureties for his good behavior, or to be otherwise restrained, conformably to the proclamation or regulations established as aforesaid, and to imprison, or otherwise secure such alien, until the order which may be so made shall be performed.

When an alien enemy is required by the President, or by order of any court, judge, or justice, to depart and to be removed, it shall be the duty of the marshal of the district in which he shall be apprehended to provide therefor and to execute such order in person, or by his deputy or other discreet person to be employed by him, by causing a removal of such alien out of the territory of the United States; and for such removal the marshal shall have the warrant of the President, or of the court, judge, or justice ordering the same, as the case may be.