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...."

Structure

Topic + 由 + Person + Verb

Examples

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.

See also

Sources and further reading

Books

Boya Chinese Lower Intermediate 2 (博雅汉语准中级加速篇) (pp. 111)
卓越汉语－公司实战篇 (p. 245)