Is the Nintendo DS region free?

Older Nintendo DS and DS Lite software is region-free, so you can play most of that software on a Nintendo DSi and Nintendo DSi XL from any region. It’s possible, however, that future Nintendo DS software will incorporate region encoding.

Is the DS and 3DS region locked?

While all 3DS software is region-locked, Nintendo DS software is not. Because that region-locking isn’t encoded into the DS software, you can play software from all regions on your 3DS.