I have been faced with a claim that Apple has disallowed the use of the "close" button in an iPad app. I have read the documentation, and -- though Apple frequently says you should try not to do it, that it frowns on it -- is there any specific statement from Apple that says that developers cannot use a "close" button?
I am not looking for a flame war --
What reference/documentation answers this question?
An app I am developing depends on the concept, so I need to know if I am going to get it rejected on those grounds. Again, I am not looking for opinions, but specific references in the docs, either pro or con.
Yes, you will absolutely be rejected. You may not programmatically quit your application. This is enforced through rule 10.1 in the App Store Review Guidelines:
10.1 Apps must comply with all terms and conditions explained in the Apple iOS Human Interface Guidelines
The relevant section of the Apple iOS Human Interface Guidelines is aptly named Don't Quit Programmatically.
Don’t Quit Programmatically
Never quit an iOS application programmatically because people tend to interpret this as a crash.
note: the docs are being annoying about direct links to subsections right now, so this is a link to the main section. The Don't Quit Programmatically" subsection is about two-thirds down the page and is accessible from the navigation panel on the left.