Is there a new /Lock

Hilo everyone I'm back. If you're wondering why I'm writing this it's because I'm no longer banned {along with redarrow1321 (no idea how we got un-banned  )}. Today I started playing on this server again!
 
I was running around the wild when I decided to make a home, so first of all I made a chest to store some rubbish to have more space to collect building materials. But, when I tried to use the old /lock (as I have been banned for about a year and am not up-to-date on current events or commands), it didn't work  . I would like to know if there is a new command for locking chest, as if there isn't I can't be bothered to start a new life on this server.
 
P.S Could anyone tell me why I'm un-banned?
 
P.P.S If there is a /lock command, could you tell me what has happened since I left?

You were unbanned as the server's ban-list got cleared a few months ago so that old players can get another chance to play.

There is no longer a /lock command as the server is now "Raid/Greif". If you would like to keep your items secure then the best way to do that is to either hide your chests, or put your valuables in an ender chest.