"France knew it couldn't stop the US.
But what it did was to show the world what the US was doing : attacking a country without UN assent."

Right, about France knowing it couldn't stop the US. Not really correct about the second part. Resolution 1441 said Saddam had to comply or face severe consequences.
" The resolution states that Iraq remains in material breach of council resolutions relating to Iraq's 1990 invasion of Kuwait and requires that Baghdad give UNMOVIC and IAEA a complete and accurate declaration of all aspects of its chemical, biological and nuclear weapons programs and ballistic missiles systems, as well as information on other chemical, biological, and nuclear programs that are supposed to be for civilian purposes, within 30 days."
http://usinfo.state.gov/topical/pol/terror/02110803.htm

If I'm remembering correctly, the UN did give assent to Gulf war I and therefore since Saddam had violated the cease fire agreement, Iraq was in essense opting to continue with this war. I'm not aware of the UN withdrawing it's assent to the war or declaring the war was at an end. In fact 1441 could be seen as a sort of a update, in which "The Security Council unanimously adopted a resolution November 8 strengthening the weapons inspection regime for Iraq and giving Baghdad, in the words of the resolution, "a final opportunity to comply with its disarmament obligations."

Instead what France did was show that it was unwilling to support a miltary action which the US was leading. If the Clinton administration had gone to the UN to get a resolution before it bombed Iraq and France had blocked it, it would have been a similar thing. The reason the US went to the UN for the second resolution, was mainly to make the Brits more comfortable, France chose not to allow the US or the Brits this comfort; and made the bogus claim that UN Charter does not sanction war [I suppose the French thinks it only sanctions empty threats or the severe frowning to show the displeasure of some diplomats:].

Of course, the US is not required to get the assent of the UN before engaging in warfare, but as far as the Gulf war II; it was with the assent of the UN- whether the French liked it or not.

I guess the only *plan* the French had was they hoped the coalition would fail in it's efforts to overthrow the Iraqi regime or that the coalition would have overwhelming problems restoring a new Iraqi regime. This seems to be a rather pointless position- they could simply abstained and "accomplished" this. Wait, I just thought of a reason why the French would oppose this. They didn't want to encourage the idea that a nation should first go to the UN before involving itself in some war. If going to the UN is seen as a mistake then with any future wars, the French govt will not get any public pressure to first go through the UN. So, that would be in French interest. Wow, that even makes sense. I wonder if this was the rationale.
It's the really just the same coin as "strengthening the UN", but it's a view from the French prospective of why they wouldn't want to strengthen the UN [I had kinda assumed the French would want to do almost *anything* to strengthen the UN].