On 7 June, the government of Belgium sent an Article 51 letter to the President of the Security Council, justifying its military action on the territory of Syria against ISIS by way of collective self-defense. The ODS link to the letter is here (S/2016/523), and here is the key paragraph articulating Belgium’s legal position:
ISIL has occupied a certain part of Syrian territory over which the Government of the Syrian Arab Republic does not, at this time, exercise effective control. In the light of this exceptional situation, States that have been subjected to armed attack by ISIL originating in that part of the Syrian territory are therefore justified under Article 51 of the Charter to take necessary measures of self-defence. Exercising the right of collective self-defence, Belgium will support the military measures of those States that have been subjected to attacks by ISIL. Those measures are directed against the so-called “Islamic State in Iraq and the Levant” and not against the Syrian Arab Republic.
Interestingly, this paragraph is taken almost word-for-word from the letter Germany had sent to the Council on 10 December 2015, S/2015/946:
ISIL has occupied a certain part of Syrian territory over which the Government of the Syrian Arab Republic does not at this time exercise effective control. States that have been subjected to armed attack by ISIL originating in this part of Syrian territory, are therefore justified under Article 51 of the Charter of the United Nations to take necessary measures of self-defence, even without the consent of the Government of the Syrian Arab Republic. Exercising the right of collective self-defence, Germany will now support the military measures of those States that have been subjected to attacks by ISIL.
Note, however, some of the differences: Belgium calls this an exceptional situation, somewhat diplomatically removes the reference to the lack of any need for Syria’s consent, even though that’s implicit in its invocation of Article 51, and adds a sentence saying that measures taken in self-defence are directed at ISIS rather than against Syria (even if Belgian airplanes are flying in Syrian airspace and discharging weaponry on Syrian territory without its consent). Both Germany and Belgium endorse a position whereby action against a non-state actor operating from the territory of another state is permitted without that state’s consent if the state lost effective control over the relevant area – this is very close to, but not necessarily exactly the same thing, as the ‘unwilling and unable’ test.
UPDATE: Many thanks to everyone contributing in the comments. I’d say that perhaps the most valuable lesson to be learned from this discussion is how all of these states are strategically using ambiguity in their various letters to the Council. They know perfectly well that the formulations that they have chosen are open to several possible interpretations, and they were deliberately chosen precisely with that in mind – not simply as a matter of diplomacy, but in order to create legal cover for what they want to do today while keeping their options open for the future. Nothing less could be expected, of course, when we bear in mind that the Council’s ISIS resolution 2249 is itself a masterful example of such a use of ambiguity. But ambiguity of this kind is also obviously detrimental when it comes to solidifying a clear position with regard to self-defence against non-state actors on the basis of state (and UNSC) practice.
In that regard, a kind reader also let me know that Norway has also sent a letter to the Council, dated 3 June, S/2016/513. The three key paragraphs are quoted below the fold – note how simply wonderful Norway is in saying nothing, beyond simply stating that it is exercising the right to collective self-defence without directing its actions against Syria.
I am writing in accordance with Article 51 of the Charter of the United Nations to report to the Security Council that the Government of Norway is taking necessary and proportionate measures against the terrorist organization Islamic State in Iraq and the Levant (ISIL, also known as Da’esh) in Syria in the exercise of the right of collective self-defence.
The Security Council recognized in its resolution 2249 (2015) that ISIL constituted a global and unprecedented threat to international peace and security and called upon Member States to prevent and suppress terrorist acts committed by ISIL and to eradicate the safe haven that ISIL had established over significant parts of Iraq and Syria. The Council reiterated that call in its resolution 2254 (2015). In that respect, the Council noted the letters dated 25 June 2014 (S/2014/440) and 20 September 2014 (S/2014/691) from the Iraqi authorities stating that ISIL had established a safe haven outside Iraqi borders in Syria that was a direct threat to the security of the Iraqi people and territory. The Government of Iraq requested the United States to lead international efforts to strike ISIL sites and military strongholds.
Pursuant to that request, the Government of Norway is taking measures against ISIL in accordance with Article 51 of the Charter of the United Nations. The measures are directed against ISIL, not against the Arab Republic of Syria.