Is it illegal to steal something back that you own?

Say something got stolen from you, in this case a digital camera. If you end up finding out who took it (the rare chance that does happen) and the authorities cannot help in the matter, can you take the camera back?

Also, what if it has been resold to an unsuspecting person and then you approach them to get the camera back?

Please do not take this too seriously – it is all hypothetical and I’m just looking for a general knowledge answer.