How to discipline a highly creative individual i?

You sometimes cannot go straight to firing.  You need to follow procedure, as well.  Verbal warnings that he acknowledges in writing, written warnings, and termination.  Is he really violating a clear written policy?  If not, and he's just annoyingly enthusiastic, there's not a lot you can do at that point.

creatively, of course.

If your employee is "highly creative" and he has directly caused the company to receive "a lot more revenue".  Why discipline him at all?  So what is the harm that he does not want to follow the chain of command -- some of the suits getting bent out of shape because their manager title being ignored, big f'**n deal.  Maybe it is the district manager's ego that should be disciplined.   As long as the work is being done your company should not put so much emphasis on an arbitrary issue like a chain of command.

In this economy where the companies who survive are the ones who can actually make money, your company has found the proverbial 'goose that laid the golden egg' a creative person who is willing to share his creativity with this company instead of going into business as its competitor.  Instead of trying to discipline this person the company should be bending over to find ways to keep him.  

Think outside the box or be prepared to lose this person to a competitor who will value him.  Make a slot for your creative person so he will NOT report to the simple-minded District Manager (who probably has zero creativity but will take the credit for the creativity of this other employee).  Create a job category for your creative person.  Work with him to come up with a job category where he will have the maximum amount of freedom and support to be creative and improve the company profits.  

This kind of thing happens all the time to simple-minded, short-lived companies who would rather tie a creative person to a "chain of command"  because "we always did it that way" instead of allowing a creative employee to spread his wings.  What is better this person being creative or being like 99.9% of employees who put in their time, follow the rules, and never give one cent extra?

You have a diamond in this creative person.   Instaed of making him follow your sophomoric chain of command rules, you should be working with him to find a spot where he can help the company grow.

Since your question is general in nature, the answer will also be general.  The person has been creative precisely because he has been thinking outside the box and not conforming to "group think" and the rigidity of "chain of command."  He must have contributed to the bottom line and probably has made more of an impact than many of the middle managers since the corporate office is not willing to let the guy be fired.    

Rather than trying to "discipline" him, in order to make him conform rather than be creative, the corporate leadership team should ask for his suggestions and try to flatten the organization structure so as to encourage more employees to be creative.  There is a well known case study of Microsoft having missed the boat on the Internet and was close becoming irrelevant.  Thanks to a creative employee and fortunately the absence of a rigid chain of command, the company re-invented itself before it was too late.  Generally speaking, successful and innovative companies have a less rigid organizational structure and allow for network effects and facilitate the flow of information and ideas within different parts of the organization.  The phrase "chain of command" does not even appear in their way of thinking.

If someone is helping your business, what would be the purpose of firing them?  If a chain of command issue is standing in the way, then you should be talking to HR about not how to fire him, but what he can do, and where a better place for him to use those talents might be.

If he is, do you think it's possible that he might go to a competitor and use those talents there?  I think it might be highly likely.