Check/ Force Disable creative mode on other players?

[Neberu]

A few friends and I started a server together and I'm the admin. We all went creative initially because we wanted to build up a neat house to live in but now the plan is to switch to survival mode and go from there. My questions is, is there a way for me to check what mode a player has thier NEI set to (survival, creative, creative+) because if I deop them and they're still in creative mode then it just locks them in creative mode. Alternatively is there a way to force them out of creative mode with a server command?

 

[darkinnit]

If they're online, you can use:
/gamemode survival playername

If they're not online, and you have access to their playername.dat files in the world/players folder, you can use a program like NBTExplorer to edit the gameType value to 0
http://www.minecraftwiki.net/wiki/Player.dat_format