Lucario is a 4th gen. pokemon, therefore not available in emerald, which is a 3rd gen game.
Riolu and Lucario are new Pokemon which live in Sinnoh so are unobtainable in the game emerald with out some sort or glitch or cheat
You can't get new Pokemon into old games. Lucario is a 4th generation Pokemon and emerald is a 3rd generation game.
You can't get Lucario in Ruby, Saphire or Emerald. Diamond, Pearl and Platinum only. sorry....
Lucario is a fighting and steel type Pokemon.
In fire red Lucario is a inexsistable Pokemon because it is a SINNOH Pokemon.
the main pokemon, ditto, or another lucario.
Lucario and the Mystery of Mew.
You have to evolve Riolu to get Lucario.
lucario a not a legendary pokemon. lucario evolves from riolu with high friendship.
Lucario was introduced in Pokemon Diamond and Pearl. It's appeared in Pokemon games since, including Pokemon X and Y which gave Lucario a Mega Evolution.
Lucario! Hope This is useful, as Lucario is a really cool pokemon. :-)