I tried doing that yesterday, and it wouldn't work! How ironic! But I think you need to get both the Ruby and Sapphire first in LeafGreen to allow trading between Ruby, Sapphire, and Emerald. I am not sure, because you can't find an Emerald in the game, but that's what my friend said. However, when I traded between his LeafGreen and my Emerald, guess what happened? Bingo, link error, that's what! From what I've heard, you need to get the National PokeDex in order to trade with LeafGreen, but you can also get the National PokeDex by trading with LeafGreen without it... weird. Maybe that only applies with Ruby and Sapphire, though. From what my friend says, you need to beat the Elite Four with at least 60 Pokemon in your PokeDex to get the National to permit trade, but I cannot promise any of this.
Owner of the formerly ranked number one Halo PC modded server in the world, FRIGID MASS CTF WAR. Joiner-friendly mods and five-minute hotfixes = loyal clientele.
Been here since February 2004. It's May 2022 as of writing this. Wish Rich would revive this place. Guess I'm only here for the nostalgia now.