Can the multiplayer function in a handheld game work with a game from a different region?

I am talking about if both players have the same game with the same multiplayer functions each from a different region. If I were to get and have one type of game from different regions, would their multiplayer functions be able to work with one another? I can't actually test this myself since I don't have any games from any countries outside of the US. I am under the assumption that both the games and the systems are region free.|||Tha depends on the device. With psp just download adhoc free on psn and you can play with anyone all over thw world. Not sure with other consoles tho