By default, killmails are private to the person who landed the killing blow, and the person who lost the ship. Either of those people may choose to allow ESI access to their mails for loss reporting to a corp or zKill, but nothing defaults to being published without someone consenting.
You mean, like the people who received the killmail, or the ones who get them shown? I think even a lawyer would have trouble defending something as “published without consenting” if the “victim” has to publish something first. You’d have an argument if people were driving to players’ homes and forcing them to publish their killmails at gunpoint, but that wouldn’t be something CCP could do something about.
To see the killmail in game, one of the two recipients has to share it. So it didn’t default to being published - one of the recipients made it available to others for access.
Have you ever heard of “Locator agents”? There are in-game NPCs that you pay a tiny fee and they’ll tell you the location of another player in minutes.