Board Thread:Questions and Answers/@comment-77.100.131.40-20140130192817/@comment-1757231-20140130204851

Unfortuantely, no. All Operators on servers can open Personal Safes, and this is a remedy that can't be fixed. The only thing you could do is use an Alchemy Bag (they're player-oriented, so people can't steal your stuff), or deop your friend.