Emphasizing the doer of an action with "you"
由 (yóu) is used to emphasize who is the doer or initiator of an action, a bit like in English where we might say: "Andy is the one who...."
Topic + 由 + Person + Verb
- 这 件 事 由 我 负责。I am responsible for this.
- 这 是 由 他 决定 的，你 就别 干涉 了。This is for him to decide, don't meddle.
- 太 悲剧 了，会议 由 王总 主持，肯定 会 很 无聊！Oh no. This meeting is being led by the head manager. It's definitely going to be boring.
Note that 由 not a passive marker.