In 2005, Iraqis approved the Constitution in a referendum, but they voted on an incomplete and badly written draft, not realising that the document would deepen Iraq’s misery. The hasty way the Constitution was drafted, the many unhelpful external interventions, the absence of Iraqi constitutional expertise and the side-lining of Sunni Arab representation have all contributed to the precarious situation in Iraq in the subsequent eight years.
Considering the myriad confusions and divisions underlying the Constitution’s drafting process, it is not surprising that the document has created more problems than it has solved. The Constitution’s vagueness and ambiguity has hindered its application.
The excessive concessions granted to the Kurds on the issues of federal government, natural resources and Kirkuk (and their subsequent refusal to renegotiate) have been a major factor in maintaining the chaotic situation that pervades most of Iraq.
Source http://www.lse.ac.uk/middleEastCentre/publications/Paper-Series/Iraqi-Constitution.aspx