While this seems to be directed at people who aid and abet terrorists, there are a couple areas that is disturbingly vague. One of the classes of people who can have there property and money seized are people, "undermining efforts to promote economic reconstruction and political reform in Iraq or to provide humanitarian assistance to the Iraqi people." The other is any person, "to be owned or controlled by, or to have acted or purported to act for or on behalf of, directly or indirectly, any person whose property and interests in property are blocked pursuant to this order."
Bush has often stated that people that vote or speak against the Iraq war are helping the enemy, and that they are hurting the reconstruction effort. Be it a protester or a congress person. So the first sectionned I mentionned before could possibly be used to stifle free speech.
And the second one sounds like it could be used to prevent people affected by this from getting legal representation.
Wile I suspect this is a stretch, I have such a deep mistrust of this administration, I can't help but believe they really would try to pull such an underhanded attack on American liberties.