The second law states that:

A robot must obey the orders given it by human beings except where such orders would conflict with the First Law.

But it says nothing about property. What if a robot owned by someone is given an order by someone else?

Surely if the same person gives contradictory orders, the last one will be executed:

Move that box upstairs. Wait no, just put it on the porch.

But what if a robot is carrying groceries outside, and someone says:

Hey you, stop what you're doing and take those groceries to my apartment.

It shouldn't agree to do that.

So, do people just say "Only obey me" when they buy a robot? Does that mean a robot ignores every order by non-owners, even if it's small help like helping an old lady cross the road? The robot would have to tell between harmless orders from strangers and orders that cause non-physical harm (like stealing their stuff, smashing their car, etc.)

If a households owns a robot, they'll say something like "Only obey me and my family", then what if orders contradict inside family members?

How does it work exactly? Is it just managed by some part of the AI less fundamental than the 3 rules?

_{I've never read Asimov, sorry if it's explained in the first chapter of the first book. I didn't see it discussed anywhere.}