While it’s a bit newer than the GBA, there is at least one Wii game with intentional anti-emulation measures: https://tcrf.net/Cars_2_(PlayStation_3,_Xbox_360,

While it’s a bit newer than the GBA, there is at least one Wii game with intentional anti-emulation measures: https://tcrf.net/Cars_2_(PlayStation_3,_Xbox_360,_Windows,_Wii)#Anti-Dolphin_Code https://tcrf.net/Cars_2_(PlayStation_3,_Xbox_360,_Windows,_W...