Ooh. Bad idea, especially when the CEO called him to tell him about the dress code. If he/she specifically tells you what the dress code is, that's a test in and of itself. Are you listening? Are you capable of adapting?
I worked for a large contracting firm in the late 90's/early 00's. They had a style guide for their consultants which recommended to appear for work and/or interviews dressed "one step higher" than the clients environment. The thought process was that the same level (especially when business casual) was you considered yourself and equal already - not necessarily a good impression when looking to get a job. Too over dressed also caused issues because you were putting yourself "above" the customer and thought you were better than them - not necessarily the truth, but it's all about perception.
So @sessions, I would suggest you listen to the CEO. If you feel uncomfortable going in jeans, then go in a pair of slacks and a button down shirt (a more traditional business casual). That keeps you looking similar to them, and shows you did listen to what they said.