Of course. Said person owns the product, so said person can do with it what they want.
That doesn't mean Apple should always go out of their way to accommodate them after they have made said choice.
I changed the battery on my car. I came back and found my car locked and disabled. Toyota said that it was done for security reason because my non-Toyota approved battery hasn't been tested (by Toyota) and could potentially explode.
Maybe attitudes towards these sorts of issues are greatly different across the pond.
No kidding! Not everyone can or want to go to Apple every time there is a problem with his/her iPhone.