I'll go with possession is nine-tenths of the law
It turns out that's not true (at least in the U.S.) You may want to talk to a lawyer about that before you get yourself in trouble.
Of course I also think if someone borrows your camera and takes a picture (for example if you are on vacation and you ask a stranger to take your picture), you own it.
I believe this is a grey area of law, see the recent athlete/fan selfie stories.
As always, do not take legal advice from anyone on the Internet unless you know for a fact the person is a lawyer with expertise in that particular field.