[ninty]

The US, in their opinion, did not properly justify the war.

1) US did not prove Saddam has any weapons, which was the original reason for war.
2) US did not prove Saddam was a threat to the US or any other country

Article 51 of the UN Charter trys to disuade countries from attacking one another without being first attacked. It is most likley that the Germans, French and many other countries objected to the war because they did not recgonize the US' pre-emption as justification for war.