Maybe your Pokemon is holding a key item, or your Pokemon might know a hm move or your game might be messed up
you cant get reggiggas in Pokemon emerald
You cant
you cant. You can only catch it in Pokemon emerald, but, you cant catch latias in emerald.
you cant its a Pokemon from emerald
Ditto
You can.
You CANT!
you cant
you cant
You cant!
you cant
Sorry But You Cant.