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.