The Ethics Ordinance
Yes, Chicago really has an ethics ordinance - on paper. This does not mean it is enforced in any way nor does it mean that it can be used for grounds to get someone off the ballot.
Rahm Emanuel, in his quest to become the Mayor of Chicago, actually did not fulfill the terms of what is required when he filed for Mayor. However, a violation of the Ethics Ordinance is not grounds for dismissal of a petition submitted by a potential candidate; Rahm was actually very coy in his submittal of information on his Statement of Economic Interest. As long as something is submitted it is apparently okay in the eyes of the Board of Elections Commissioners.
Here is the link to the Ethics Ordinance.