Riley is a character from the Pokemon Diamond and Pearl anime, not Pokemon Galactic Battles. He's a fisherman from Snowpoint City and a skilled Pokemon trainer who specializes in water types. He is most notably the trainer of the powerful Gyarados that Ash faces in the Sinnoh League.
Pokemon Galactic Battles is a film that features a completely different storyline and characters compared to the main Pokemon Diamond and Pearl series, which is where Riley appears.