Are Nintendo DS games region encoded?

Question

Can games for the DS only be played in the area in which they have been purchased, for example will a game purchased from the US work on a system purchased in Japan or the UK

Answer 1

there are no NTSC or PAL region codes

however, there are the following words on the back of many, if not all, DS gamecases

""FOR SALE, RENTAL AND USE ONLY IN USA, CANADA, MEXICO AND LATIN AMERICA.""