The developer license agreement states this very clearly. Apple does not publish this agreement, but you can get yourself a copy easily.
Versions of it have been published on the web from time to time, e.g. By the EFF:
https://www.eff.org/deeplinks/2010/03/iphone-developer-progr...
The text in question is: Apple may change the Program Requirements or the terms of this Agreement at any time. New or modified Program Requirements will not retroactively apply to Applications already in distribution. In order to continue using the Apple Software or any services, You must accept and agree to the new Program Requirements and/or new terms of this Agreement. If You do not agree to new Program Requirements or new terms, Your use of the Apple Software and any services will be suspended or terminated by Apple. You agree that Your acceptance of such new Agreement terms or Program Requirements may be signified electronically, including without limitation, by Your checking a box or clicking on an "agree" or similar button. Nothing in this Section shall affect Apple's rights under Section 8 below.