U.S. SALES ONLY
Purchases or rentals (as applicable) from the iTunes Store are available to you only in the United States and are not available in any other location. You agree not to use or attempt to use the iTunes Store from outside of the available territory. Apple may use technologies to verify such compliance.
Users also agree that:
CONTENT USAGE RULES
Your use of any Products purchased or rented (as applicable) from the iTunes Store is conditioned upon your prior acceptance of the Terms of Service, including, without limitation, the Usage Rules set forth therein.
By violating these terms of sale users risk having their accounts terminated and, as a result, they could lose the ability to play back content they have bought from the iTunes Store. On the other hand, if users have purchased music free of digital rights management software (typically from the iTunes Plus collection which is set to expand to encompass all iTunes music in the next few months), they may retain the ability to play this music back as before. The Termination clause in the terms of service makes the consequences of not complying with the terms of sale and terms of service quite clear:
a. Termination by Apple. If you fail, or Apple suspects that you have failed, to comply with any of the provisions of this Agreement, including but not limited to failure to make payment of fees due, failure to provide Apple with a valid credit card or with accurate and complete Registration Data, failure to safeguard your Account information, violation of the Usage Rules or any license to the software, or infringement or other violation of third parties' rights, Apple, at its sole discretion, without notice to you may: (i) terminate this Agreement and/or your Account, and you will remain liable for all amounts due under your Account up to and including the date of termination; and/or (ii) terminate the license to the software; and/or (iii) preclude access to the Service (or any part thereof).
b. Termination of the Service. Apple reserves the right to modify, suspend, or discontinue the Service (or any part or content thereof) at any time with or without notice to you, and Apple will not be liable to you or to any third party should it exercise such rights.
The reason why such purchases are illegal (or at least contrary to the iTunes terms of sale and their terms of service) is that content "purchased" from the iTunes Store is "provided to you by way of a license only". There is a common misconception that when you buy a CD, DVD or, in this case, digital music, you become the owner of that item. In fact, what you are buying is a license to consume that media in a particular way. Digital rights management software (or "DRM") adds a layer of complexity to the content license and usually prevents the consumption of that content using certain devices. A good example of DRM in action is how you can't play non-iTunes Plus purchases from the iTunes Store in a version of iTunes registered using someone else's iTunes account.
Part of that licensing regime likely includes limitations as to where iTunes music may or may not be sold and those limitations are probably dictated by the music industry. In fact it is probable that all the limitations on the sale and consumption of the content are dictated by the music industry. The bottom line, though, is that buying music from an iTunes Store like the US iTunes Store from here in South Africa is certainly a violation of iTunes' terms of service and terms of sale and because it likely constitutes a copyright violation, it is also illegal.