In the ancient world, as a rule, wealthy landowners hired shepherds to take care of *their* sheep. In other words, a shepherd could talk about "his sheep", but he wasn't their owner. In that sense, not even Jesus strictly claimed to possess his own (metaphorical) sheep, because even though he was Lord, and even though he did call them "my" sheep, he was also the Righteous Man who did everything on behalf of Another.
In the ancient world, if someone ever died to protect sheep, it probably wasn't the sheep's owner. Instead, the one who might have to die while protecting the sheep is a shepherd, who was hired by the owner. The owner who hired a good shepherd would expect that good shepherd to protect *His* sheep with his life. And the shepherd would risk everything right up to death, because the shepherd owed his own life to the owner whose sheep brought them both of their livelihoods.
In Jesus' case, especially, the only reason the Good Shepherd would lay down his life for "his" sheep, was because they belonged to the One whom the Good Shepherd most cared about pleasing.
All sheep need shepherds, but - and I'm talking about churches now - christian shepherds should never think of "their" sheep as *theirs*. If there's anything at all scriptural about the way someone might pastor one of God's flocks, that shepherd should only feed and protect sheep on behalf of Another.
(H/T - this post was sparked by a FB thread underneath Alan Knox's latest post.)