A grunt will drop it
you get the galactic key from that undercover officer when he finds it in galactic warehouse or you need to find it in the warehouse or the galactic hq. there both in veilstone city. you will find a item in the warehouse that might be it because i forgot
the first galactic key is in the galactic warehouse
in the vilstone warehouse next to the galactic building
In the Galactic warehouse. 0.0
the galactic key is in somewhere in the game N.M.I
At the end of the Galactic warehouse
you have to get the secret key
You find it in the Galactic Headquarters after they capture Azelf, Uxie, and Mesprit.
talk to the team galactic guy in front of the team galactic building.(In veilstone city)
When you have got the galactic key from the warehouse then you need to go to the other side where you got the warehouse key.use the galactic team to open the door and then you need to find out where the boss is located.then u free the 3 legendary pokemons!
In the galactic warehouse to the left of the Galactic HQ
First there should be a galactic grunt outside the headquarters. Talk to him to get the key to the warehouse. Go to the warehouse which is also in veilstone city. In the warehouse you should find the key to the headquarters.