GBA is the same everywhere in the world so yes, it should work in theory.
I have ordered an Action Replay online (PAL) (what with me being Australian) (it has a Freeloader function) and am planning to order Colosseum as well. Would an Australian copy of R/S in an Australian GBA be compatible with an American copy of Colosseum on an Australian GC??? (Remember, the Action Replay has a Freeloader function)
GBA is the same everywhere in the world so yes, it should work in theory.
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^ Better do what he says, he's crazy! ^