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National Security v. International Law in the Wake of the Paris and Brussels Attacks

By Ayat Mujais

After the recent terror attacks on Brussels and Paris, there has been a push from numerous nations, such as the United States and France, to increase the use of force against the Islamic State of Iraq and the Levant (“ISIL”) in order to eradicate the dangers that it poses to national security. Both countries have already claimed that ISIL poses a major national security risk and have used force in Syria and Iraq to fight ISIL.[1] However, there has been backlash from various legal scholars who have determined that using force against ISIL to protect national security, particularly in Syria, is a violation of international law and the UN Charter.[2] This raises the important question of how to balance national security concerns against international law in the wake of extremists groups such as ISIL.

Article 2(4) of the U.N. Charter states that “All members shall refrain…from the threat or use of force against…any state”.[3] Although ISIL is not itself a “state”, ISIL resides within the territories of Syria and Iraq; therefore, any attacks on ISIL within either state essentially is an attack on the states’ territorial integrity. So how can one justify attacking ISIL? For countries such as France and Belgium, the answer is simple. The U.N. Charter provides in Chapter VII an exception, one that allows military intervention for the sake of self-defense if there is a threat of an imminent armed attack.[4] Because ISIL has succeeded in attacking cities in both France and Brussels, these states can justify using force without violating international law by claiming that they are acting in self-defense and protecting their national security.

The question is where does this leave states like the United States, who has claimed self-defense in order to use force against ISIL, but had not had an armed attack from ISIL within its borders. Many say the U.S. use of force against ISIL has been in violation of international law due to lack of justification under both traditional and customary international law – the United States lacks state consent from Syria[5] or from the Security Council[6] to use force on Syrian territory, and claims of humanitarian intervention[7] and anticipatory self-defense[8] are not viable. The only potential successful legal argument would be for the United States to claim self-defense of their national security.

To prove an armed attack is imminent for the sake of self-defense, the probability of an attack must be 100%.[9] However, the emergence of ISIL and its ability to carry out attacks on states at any time brings a new challenge to the concept of imminence. ISIL has proven that it will carry out its threats of attacks, as was seen with the incidents in Paris and Brussels.[10] Indeed, ISIL has threatened to attack the United States through proxies within the United States.[11] However, there is not 100% probability that ISIL will actually carry out these threats in the near future. It is possible that due to the fact that ISIL is by far the richest and most technologically advanced terrorist organization of its time, the concept of imminence under the right to self-defense is shifting to allow more leeway in states using force against ISIL in the name of national security, even without finding that there is 100% probability of an armed attack.[12]

This view is supported by the fact that the U.N. Security Council adopted Resolution 2249 this past November, which calls for “all necessary measures” to eradicate ISIL.[13] Although this Resolution does not provide a legal basis or authorization for the use of force, it does show that the use of force against ISIS may be permissible in self-defense of a state’s national security, especially in the wake of attacks such as those in Paris and Brussels.[14]

[1] Jethro Mullen and Margot Haddad, ‘France is at war,’ President Drancois Hollande says after ISIS attack, CNN (Nov. 16, 2015),; Letter from the President – Authorization for the Use of United States Armed Forces in Connection with the Islamic State of Iraq and the Levant,

[2] Theo Farrell, Are the US-led air strikes in Syria Legal – and what does it mean if they are not?, Telegraph, Sept. 23, 2014,

[3] U.N. Charter art. 2(4).

[5] Theo Farrell, Are the US-led air strikes in Syria Legal – and what does it mean if they are not?, Telegraph, Sept. 23, 2014,

[7] David Kaye, The Legal Consequences of Illegal Wars, Foreign Affairs, August 29, 2013,

[8] Richard A. Falk, What Future for the UN Charter System of War Prevention?, 97 Am.  J. Int’l L. 590 (2003),

[9] John C. Yoo, Using Force, 71 U. Chi. L.Rev. 1 (2004),

[10] Catherine E. Shoichet et al., New ISIS video threatens France, Italy, U.S., CNN (Nov. 19, 2015),

[11] Lee Ferran and Rym Momtaz, ISIS Trail of Terror, ABC News (Feb. 23, 2015),

[12] Michael P. Scharf, How the War Against ISIS Changed International Law, 48 Case Western Reserve J. of Int’l L. 1 (2016),

[13] S.C. Res. 2249, U.N.Doc. S/RES/2249 (Nov. 20, 2015),

[14] Michael P. Scharf, How the War Against ISIS Changed International Law, 48 Case Western Reserve J. of Int’l L. 1 (2016),


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