However there is something no one seems to be saying and it is THE ONLY justification for an invasion. When Iraq was defeated in the Gulf War they surrendered and sued for peace. The U.S. said they would stop hostilities under certain conditions such as weapons inspections, no fly zone and a few others. If Iraq decides not to honor their agreeements then the U.S. is no longer obliged by its agreement to halt hostilities.
I am very big on people honoring their agreements.