Wasn't it her job to at least know where the gray areas where? If you know you're in a gray area, I'd expect you know that you _might_ be breaking the law.
The point of the story is that social proof isn't enough when it comes to legal matters. The author contrasts his behavior with Michelle's to point out what can happen when you use social proof rather than direct legal advice.
From what I can understand from the post, Michelle's plan was reviewed by PwC with no findings. So I guess she believed that the gray areas were clarified.
Btw I fully agree with you.
That sounds like a recipe for chilling effects to me.