Vattel, is it true (1758), ventures to lay down that--
"Le Souverain qui déclare la guerre ne peut retenir les sujets de ennemi qui se trouvent dans ses états au moment de la déclaration ... en leur permettant d'entrer dans ses terres et d'y séjourner, il leur a promis tacitement toute liberté et toute sûreté pour le retour."
And he has been followed by some recent writers. There is, however, I venture to hold, no ground for asserting that this indulgent system is imposed by international law. I am glad, therefore, to find the Attorney-General laying down that--
"for strictly military reasons, any nation is entitled to detain and to intern soldiers found upon the territory at the outbreak of war."
And I should be surprised if, under all circumstances, as the learned Attorney-General seems to think probable--
"England would follow, whatever the strict law may be, the humane and chivalrous practice of modern times, and would give to any subjects of a hostile Power who might be found here engaging in civilian pursuits a reasonable time within which to leave for their own country, even although they were under the obligation of entering for service under the enemy's flag."
The doctrine of Vattel has, in fact, become less plausible than it was before universal liability to military service had become the rule in most Continental countries. The peaceably engaged foreign resident is now in all probability a trained soldier, and liable to be recalled to the flag of a possible enemy.
There may, of course, be considerable practical difficulties in the way of ascertaining the nationality of any given foreigner, and whether he has completed, or evaded, the military training required by the laws of his country. It may also be a question of high policy whether resident enemies would not be a greater danger to this country if they were compelled to remain here, than if they were allowed, or compelled, to depart, possibly to return as invaders.
I am only concerned to maintain that, as far as international law is concerned, England has a free hand either to expel resident enemies or to prevent them from leaving the country, as may seem most conducive to her own safety.
I am, Sir, your obedient servant, T. E. HOLLAND. Oxford, February 25 (1909).