Now, to get somewhat anal about all of this, did you check the status of the cases to see if they're all "good law"?
For number 2, are you intending to marry for money, but don't? (Which makes sense...thought crimes aren't yet illegal.)
The thing that I'm tripping over on the rule is the part from case 1 and 2, which is somewhat densely (as in language, not a value judgment on the writer) constructed as a negative.
For myself, I'd probably go something more like:
An individual is not guilty of marriage fraud if he or she enters into a marriage, and that marriage is not solely for the purpose of evading immigration laws, regardless of specific knowledge of those laws.
Which is, I admit, much closer to a negative version of what the statute says.
So, this says "they got married" and "not just to evade INS laws". I'm trying for an implication that the other reasons are legitimate, but that would probably have to be spelled out more completely.
I'm not sure if this helps or not, but it's certainly gotten me thinking this morning.