If its locked then that means you didn't finish the legendary pokemon hell yet.

If you don't know what to do then if team aqua/magma has already used the orb go to the
northern part of sootopolis and meat up with Steven and wallace (wallace is the gym
leader, is locked because he isn't there).

If you havnt seen team aqua/magma use the orb then go to route 126/127 and look for a
circle in the water you can walk on with a dive spot in the center and south. go in south.
this i where all the legendary stuff starts to happen.

And if you nothing about an orb then its a wonder you even got to sootopolis. haha. if you
haven't done the orb stuff then make sure you have these TM/TH's active with you, surf,
dive, strength and rock smash. also have a master ball with you if you want to catch the
legendary. if you want it then save before righting it. once it faints you can never get
it again. if it dies simply reload your file. :) if you need more help email me.
red_wish@hotmail.com

you have to beat groudon or catch him. if you can't do that you have to get into your
enemy team's base and beat ther leader