But, of course, there's about one zillion more places (including online) to shop for video games besides Circuit City & Best Buy. With most of them not giving two squirts what your age is.
Quite a bit fewer than that, actually, and most of them will be on-line; nearly all the "chain" brick-and-mortar stores either won't sell AO games (GameStop, Circuit City and Best Buy are among those that won't) or require IDs for them.
Further complicating the search for the freshly-minted AO version of San Andreas - Take Two stopped pressing the disks for all 3 versions.