We've said it before; so has IGNPocket. Now IGNPocket has their GBAs and make 100% sure that US games can be played on import GBAs.
IGNPocket are some lucky mofos. While members of our staff have yet to get their GBAs, IGNPocket has already secured a couple new systems. Although we've said it a few times in the news and in our our GBA FAQ. IGN Pocket's GBA FAQ has stated this too. Still, there are people confused.
Well, IGN Pocket has whipped up a nice story detailing how the Game Boy Advance does not have a territorial lockout. The article is totally in-depth and should put anyone's fears to rest. (I hope!)
Clearly, the question is not "should I import the GBA" but is "how & where am I going to get my hands on one?"