If there is a disclaimer saying that all questions were written in house, then those students can't form the mental intent to break the law. If the disclaimer is just lip service, the student could still intend to cheat knowing the disclaimer was there just to provide "cover", but at that point, it becomes a proof issue.
How do you prove that a student really knew that the questions there were from the real GMAT if the website states "All of our questions are written by us. These are not real GMAT questions."
You can't negligently break a specific intent law. There are laws that require you to intend to do the action or cause a certain result. This situation is all about the intent of the visitor to the cheating website.
If a person intended to gain an advantage, that's not a person with integrity that a top school should want and each person should be kicked out or denied admission.
But I think it's GMAC pushing people around trying to make their case seem stronger than it really is. They may be right and these people intended to cheat...but unless I can see their proof these people intended to cheat, their case appears to be weak.