"Your attack on Han Blix's legal expertise is without merit. He is an acknowledged expert on international law. "

Ok, it does appear he should have the required knowledge to know what international law is. Let's look at what he said:

"Mr Blix said that while it was possible to argue that Iraq had breached the ceasefire by violating UN resolutions adopted since 1991, the "ownership" of the resolutions rested with the entire 15-member Security Council and not with individual states. "It's the Security Council that is party to the ceasefire, not the UK and US individually, and therefore it is the council that has ownership of the ceasefire, in my interpretation."
He said to challenge that interpretation would set a dangerous precedent. "Any individual member could take a view - the Russians could take one view, the Chinese could take another, they could be at war with each other, theoretically," Mr Blix said. "
http://news.independent.co.uk/uk/politics/story.jsp?story=498039

Let's say 15 people own a boat or a piece of property. Unless otherwise qualified/limited, what that generally means is that any of the 15 people can use the boat or property. Hence, what Blix is saying is this means is that the Russians could want to use the boat at the same time that the Chinese want to use the boat- therefore a potential conflict.
Therefore *his solution* is that all members must agree who can use the boat.
This is not the only "solution" therefore at very least this is debatable. Blix is talking about "theoretical" & "his interpretation". And then says it's illegal. He is not the Judge, no one appointed him to create laws, therefore it's not correct for him to say it is illegal. In order to qualify to be illegal, it needs to violate an existing law- not what he thinks should be the future law.

What others say:

"All right, let's go over this again. UNSC resolution 678 (1990) authorised armed force against Iraq. UNSC resolution 687 (1991) set the terms of a cease-fire between the members of the 1991 Coalition and Iraq. UNSC resolution 1441 (2002) affirmed that Iraq was in "material breach" of its obligations under resolution 687 and gave it one last chance to comply, which Iraq failed to do. Since Iraq had violated the terms of the cease-fire, the other parties to the cease-fire were therefore justified in resuming hostilities. The weak link here is arguably 687, since the UN Security Council declared the cease-fire between the members of the Coalition and Iraq and therefore, or so the argument goes, it is up to the UNSC to authorise resumption of hostilities. But is that really the case? The sneaky bit about the wording of 687 is that the cease-fire is not between the UNSC and Iraq, but between the members of the Coalition and Iraq; the cease-fire is merely brokered by the UNSC (and its agent, the Secretary-General of the UN). Now, I believe you're going to be very hard-pressed indeed to find a legal precedent of a cease-fire agreement entered into by two parties where a resumption of hostilities by one party in response to a violation by the other first had to be approved by whoever brokered the agreement.
.....
This was, in broad terms, the argument wielded by the government of the United Kingdom (and declared valid by its Attorney-General), and also that of the United States...
http://normblog.typepad.com/normblog/2004/01/the_iraq_war_an.html

"This has been the longstanding position of the United States and has been reflected in the Security Council's practice since UNSCR 687 was adopted in 1991. When coalition forces used force against Iraq in 1993 in response to Iraqi violations, the UN Secretary General stated publicly that the coalition "had received a mandate from the Security Council according to resolution 678, and the cause of the raid was the violation by Iraq of Resolution 687 concerning the cease-fire. So, as Secretary General of the United Nations, I can say that this action was taken and conforms to the resolutions of the Security Council and conformed to the Charter of the United Nations." No new resolution authorizing "all necessary means" was deemed necessary. "

So here you have the UN Secretary General stating the 1993 attack was legal without first requiring UN permission. This supports the notion that one or a few member can act without all 15 members agreeing and therefore this has actually set a legal precedence.

"From: John B. Bellinger, III
Date: April 10, 2003

The United States has clear authority under international law to use force against Iraq under present circumstances."
http://www.cfr.org/publication.php?id=5862

Some commentary here:
http://www.worldpress.org/specials/iraq/
More commentary:
http://www.law.unimelb.edu.au/icil/topics/iraq/resolve.htm