Memorandum from Michael Rynne to Joseph P. Walshe (Dublin)
'Theory and Practice relative to Belligerent Aircraft and Crews'

1. Strictly speaking, that is, in theory, this country takes the line that, as a neutral State, it must prevent belligerent military aircraft from overflying Irish territory or territorial waters. As the logical corollary to this, it is the rule that whenever belligerent military aircraft make a landing within Irish jurisdiction they and their crews (if surviving) are interned for the duration of the hostilities.

2. These theoretical rules conform to the requirements of international law as deducible from the relevant conventions and the practice of States generally since aircraft first became a weapon of war twenty-five years ago. All the most authoritative legal writers urge the necessity of such rules, to which they generally admit no exceptions (such as force majeure, error, etc.).
[matter omitted]

4. The strict rules laid down by pre-1939 text books and our own theoretical code which was meant to conform therewith, have undergone some modification during the last few years. It would be true to say that we still recognise a general obligation to prevent belligerents from over-flying Irish territory, and, from time to time, demonstrate our sincerity of purpose by firing on planes which persist in hovering over posts where anti-aircraft guns are in position. Also we still maintain a general right (founded in international duty) to intern foreign airmen who land on Irish territory or in the maritime belt. Scores of such airmen have been interned at the Curragh. But, while endeavouring to adhere consistently to rules of theory, we are now admitting certain classes of cases as exceptional and not involving the enforcement of the rules.

5. International law in respect of air warfare [matter omitted] is largely based on the practice of States. That law is bound to evolve according as practical changes are gradually introduced in apparent defiance of old, but perhaps, unworkable theories. Hence in recognising defensible exceptions to the strict 1914-18 rule regarding the internment of belligerent airmen and their planes, this State is not breaking but making international law. Insofar as the few remaining neutral States appear to have also recognised some exceptions to the old rules, it may be said that we are supported by precedents. However, the main fact is that the exceptions admitted by Ireland in favour of one belligerent have not so far formed the subject of a formal protest from his enemy. That we may take as meaning that all the belligerents acknowledge the justice of the exemptions made by us and rely upon our extending them impartially (asin duty bound) to all forces engaged in the present war.

6. Broadly indicated, there are only two kinds of cases where landings are made by belligerent military planes and where we do not intern the crews and planes. The first of these cases is that where the plane involved is being used as a training plane only and its crew, presumably, engaged only in training exercises. The second case is where a plane, although armed and ready for action, carrying, perhaps, an armed and uniformed crew, is able to satisfy our military authorities that it is not coming out of or going into action. 'Action' may be held to include such unwarlike activities as weather reporting or reconnaissance, but this remains to be seen when appropriate practical cases arise. So far 'non-operational' (i.e. exempted) flights have mainly been flights for the purposes of testing new machines or 'ferrying' flights of new machines from America to Europe.

In other words all the planes and crews (of both excepted classes) which we have so far released may be argued to have been taking no active hostile action against their enemies when circumstances forced them to land here. Hence we may base our leniency on a proposition something like the following:-

It is the duty of neutral States to prevent their territory being used as a base by one belligerent for operations directed against the other. Neutral territory is being so used whenever a belligerent, in order to ensure a safer or more expeditious starting point for his attack upon his enemy, or to secure for himself the element of surprise in ambushing his enemy chooses to launch operations from neutral territory instead of from his own territory. In order to prevent such unfair advantage being taken by one belligerent, (concealing oneself behind an internationally recognised neutrality is like concealing one's armed forces beneath the Geneva Red Cross), the neutral must either exclude the unfair belligerent or catch him and lock him up. Neutral territory is likewise being used as a base whenever a belligerent enters upon it to escape pursuit or avoid action with his stronger enemy. If he had not sought refuge in neutral territory (which the other belligerent is presumably too honourable to infringe) he would have fallen victim to his enemy. A neutral State must also insist on preventing this sort of thing.

But when a plane, although a belligerent military machine, finds itself on neutral territory by a pure accident due neither to the desire of its crew to use that territory as a base nor to their need to treat it as a refuge, is there any obligation on a neutral Government to take drastic action?

Given the condition of strict impartiality and, of course, the condition that the belligerent plane and crews depart, within a reasonably short time, from the neutral country, it would seem possible to answer the foregoing question in the negative.

7. In order to expedite the early departure of exempted foreign planes from Ireland, it has sometimes happened that they were allowed to repair and refuel here. This practical measure can scarcely be dispensed with and may be called for again, in future cases. It might be well to treat it always as a practical measure merely and not as a normal legal right. That is to say, it might be a mistake from the legal point of view to endeavour to assimilate military aircraft to naval vessels, which are entitled by international law to traverse neutral waters at any time and, in case of distress or shortage of fuel, to enter neutral ports for repairs etc. Apart from the overwhelming weight of legal opinion against any assimilation of aircraft (even hydroplanes) and ships, the recognition of such assimilation would almost certainly involve abuses and consequent embarrassment. It is one thing to allow an occasional ship into a 'controlled port' and quite another to have a number of unheralded foreign aircraft landing in all sorts of unexpected places throughout Ireland.