The U.S. rationale for the Iraq War has faced heavy criticism from an array of popular and official sources both inside and outside the United States. Putting this controversy aside, both proponents and opponents of the invasion have also criticized the prosecution of the war effort along a number of lines. Most significantly, critics have assailed the U.S. and its allies for not devoting enough troops to the mission, not adequately planning for post-invasion Iraq, and for permitting and perpetrating widespread human rights abuses. As the war has progressed, critics have also railed against the high human and financial costs. Some academics see such costs as inevitable until US foreign policy turns away from expanding US hegemony. Professor Chip Pitts asserts that an American empire exists, but argues that it is profoundly at odds with better instincts of US citizens and policymakers, and that rejecting neo-colonialism by military means as employed in the Iraq War is a prerequisite to restoring domestic civil liberties and human rights that have been infringed upon by an imperial presidency – while crucial, as well, to promoting peace and stability in the Middle East and other places of vital US interest. The Center for Public Integrity alleges that President Bush's administration made a total of 935 false statements in a two-year period about Iraq's alleged threat to the United States. Government expenditures A British investigation (Panorama, 9 June 2008) estimates that around $23 billion (£11.75 billion) may have been lost, stolen or not properly accounted for in Iraq. The United States Department of Justice has imposed gagging orders that prevent further investigation. International law The use of force by a state is prohibited by Article 2 (4) of the UN Charter. The only exceptions are with Security Council authorization under Chapter VII, which was not obtained, or in self-defense against an armed attack by another state under Article 51. The US government stated that an armed attack by Iraq did occur against the US and its coalition partners as demonstrated by the assassination attempt on former US President George H. W. Bush in 1993 and firing on coalition aircraft enforcing the no-fly zones over Northern and Southern Iraq since the 1991 Gulf War ceasefire agreement. Under Article 51 of the UN Charter, the US reserved the right to self-defense, even without a UN mandate, as were the cases in the bombing of Iraq in June