Here is the President’s War Powers Resolution letter sent to Congress today with notification of the use of force in Syria against ISIL.  And here is the corresponding letter about the use of force against the Khorasan Group.  The President’s statement from the South Lawn is here.

Also today, Representative to the U.N. Samantha Power sent this letter [pursuant to Article 51 of the U.N. Charter] to Secretary-General Ban Ki-moon concerning the international law justification for the U.S. and allies’ use of force in Syria:

September 23, 2014

Excellency,

In Iraq’s letter to the United Nations Security Council of September 20, 2014, and other statements made by Iraq, including its letter to the United Nations Security Council of June 25, 2014, Iraq has made clear that it is facing a serious threat of continuing attacks from ISIL coming out of safe havens in Syria.  These safe havens are used by ISIL for training, planning, financing, and carrying out attacks across Iraqi borders and against Iraq’s people.  For these reasons, the Government of Iraq has asked that the United States lead international efforts to strike ISIL sites and military strongholds in Syria in order to end the continuing attacks on Iraq, to protect Iraqi citizens, and ultimately to enable and arm Iraqi forces to perform their task of regaining control of the Iraqi borders.

ISIL and other terrorist groups in Syria are a threat not only to Iraq, but also to many other counties, including the United States and our partners in the region and beyond. States must be able to defend themselves, in accordance with the inherent right of individual and collective self-defense, as reflected in Article 51 if the UN Charter, when, as is the case here, the government of the State where the threat is located is unwilling or unable to prevent the use of its territory for such attacks.  The Syrian regime has shown that it cannot and will not confront these safe-havens effectively itself.  Accordingly, the United States has initiated necessary and proportionate military actions in Syria in order to eliminate the ongoing ISIL threat to Iraq, including by protecting Iraqi citizens from further attacks and by enabling Iraqi forces to regain control of Iraq’s borders.  In addition, the United States has initiated military actions Syria against al-Qaida elements in Syria known as the Khorasan Group to address terrorist threats that they pose to the United States and our partners and allies.

I request that you circulate this letter as a document of the Security Council.

Samantha J. Power

His Excellency
Mr. Ban Ki-moon
Secretary-General of the United Nations
New York, NY

[UPDATE:  Later today, Secretary General Ban Ki-moon offered some words that tend to support the “unable” theory that Power invoked in her letter:

I am aware that today’s strikes were not carried out at the direct request of the Syrian Government, but I note that the Government was informed beforehand.  I also note that the strikes took place in areas no longer under the effective control of that Government.   I think it is undeniable – and the subject of broad international consensus – that these extremist groups pose an immediate threat to international peace and security.]