Whether a U.S. lead invasion of Iraq is necessary or not the United States has that right and here is why.
In 1990 the U.N. security council authorized the use of military force to expel the Iraqi army from Kuwait. British and U.S. forces were the dominant contributors to the coalition.
General Powell was the Chairman of the Joint cheifs at that time. Even though the Iraqi army had not been totally obliterated at that time Powell was concerned how we might look in the aftermath. He felt that we might look evil in some way because it was TOO EASY to kill the Iraqi army. They were entirely unable to defend themselves from us.
So as an act of MERCY we offered the Iraqis a CEASE FIRE AGREEMENT. That is not a peace treaty. It means we will stop blowing you out of the sand IF you do certain things. We held up our end of the deal. We were authorized by the agreement to enforce a NO FLY zone. But the Iraqis have continued to SHOOT at us since 1992. They were obligated to destroy and document all their weapons of mass destruction. We have proven that Saddam Hussein has done all he can to avoid this part of the agreement.
The war that was fought in 1991 did not end in 1991. We (US) put the war ON HOLD. The Iraqi government has defied the agreement that put it on hold for over 10 years. The United States has done all it is obligated to fulfill the cease fire agreement. Under International law the US has the right to march its forces in peacfully and disarm Iraq. The Iraqi dictator has stated that he will fight off the invaders until the last drop of Iraqi blood has been shed. The United States has in its war doctrine that opposition is bombed first and then attacked from the ground.
So yes, the US will bomb Iraq and it is within its rights to do so.
Personally I don't think that it is that necessary, but if you don't act then you send the wrong message to other renegade countries.