Some access rights weren't set properly, meaning that non-trusted players couldn't lock their chests and doors. This has been fixed.
As a reminder, everyone is able to lock their chests, doors, furnaces and trapdoors to prevent other people from going through them. To do that, type in /cprivate while near the object to lock, then left-click it to apply the setting. If the game complies that it's already locked, or if you want to remove the protection, type /cremove. As an extra, to set an object to be available to everyone yet only lockable by you (for example, to have a chest full of items free for the taking), use /cpublic.