What impact has 9/11 and thesubsequent war in Afghanistan had on the right of self-defence?Are states now allowed to use force in responseto terrorism committed by non-state actors? If yes, how has international law responded to this recent development?
Prior to 9/11, the right to use of force in self-defense against terrorism was controversial. One major incident prior to 9/11 occurredin 1998 when the United States attacked an Al-Qaida terrorist trainingcamp in Afghanistan and a factory in Sudan claimed to be producing chemical weapons. This was a response to the bombing of the United States’ embassies in Kenya and Tanzania, whichthe United States blamed on Al-Qaida. According to the United States,it had acted in self-defense to ‘prevent these attacks from continuing.
However, since 9/11, the law on the use of self-defense in response to international terrorism has undergone significant change. Thepredominant view before then was that terrorist attacks committed by private or non-state actors were a form of criminal activityto be combated through domestic and international criminal justice mechanisms. This recent development has further challenged some of the principles limiting the scope of self-defense.
The Security Council passed Resolutions 1368 (2001) and 1373 (2001) condemning the attacks on the U.S.A. The preamble of the resolution also affirmed the right to self-defense in response to a terrorist act for the first time, though the extent to which this was an endorsement for subsequent U.S military action has been questioned.
The U.N charter is open to evolution, and the resolutions are viewed as an authoritative interpretation of the scope of Article 51. Subsequent state action also supports the position that terrorist attack now falls within the scope of Article 51 and can trigger a state’s right to self-defense. The right of self-defense is one of only two exceptions to the general prohibition on the use of force contained in Article 2(4) of the UN Charter.
Following 9/11, the U.S undertook military action in Afghanistan. Informing the Security Council, the U.S cited the decision of the Taliban regime to allow parts of Afghanistan that it controls to be used by this organisation as a base of operation. Although the U.S did present material suggesting a more substantial link between the de facto Taliban regime and the Al Qaida, it argues that the more harboring of international terrorists justifies an attack against a state.
In conclusion, 9/11 resulted in a modification of customary international law and a lowering of the threshold of state responsibility. According to Garwood-Gowers, by accepting the legality of using force in self-defence against the Taliban and Al-Qaida following 9/11, the international community recognised the existence of an expanded right of self-defense that permits the use of military force against statesthat host or harbour non-state terrorist groups that have already committed serious attacks.
Catch you around!
 See generally J Lobel, ‘The Use of Force to Respond to Terrorist Attacks: The Bombing of Sudan and Afghanistan’ (1999) 24 Yale Journal of International Law 537; R Wedgwood, ‘Responding to Terrorism: The Strikes against bin Laden’ (1999) 24Yale Journal of International Law 559.
 However, Russia, Pakistanand the Arab states condemned the action, but no formal action was taken by neither the Security Council nor the General Assembly.
 When the United States and a coalitionof allies launched a military campaign in Afghanistan followingthe 11 September 2001 (hereafter ‘9/11’)terrorist attacks, there was virtually unanimous international support for the use of force.
 The other exception is enforcement action authorised by the UN Security Council under Chapter VII of the Charter of the United Nations.
 This provisionalso forms part of customary international law, regarded as a principle of jus cogens. See Case Concerning Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits)  ICJ Rep 14 .
 A. Garwood–Gowers, Self-Defence against Terrorism in the Post-9/11 World, Queensland University of Technology Law and Justice www.eprints.qut.edu.au. Accessed February 8, 2013.