Police have a job to do. If they locate a stolen vehicle then they are obliged to at least commence to carry out an investigation for the offence of UUMV. That's because usually they wouldn't know the vehicle was stolen unless it had been reported as such, so thereby, they have to act on that complaint. If they locate a stolen vehicle and it hasn't been reported stolen then they will normally try to contact the registered owner, who, I have no doubt would be asked by the police to sign a request that no further investigation be made into the matter, if the owner didn't want the police making further investigations to try to find the offender. What Cobra is saying is quite correct. Police make investigations and based on those investigations they make a decision whether there is sufficient evidence to continue further with the investigation on the strength of the evidence they have. If there is insufficient evidence to continue to search for the offender then the matter is not closed it is simply left open as there may be further developments in the future. If an owner was foolish enough to insist on no further investigation of the matter by police then you can rest assured he wouldn't have a leg to stand on if he made an insurance claim (and who knows what unseen mechanical damage could have been caused). Unfortunately, by the simple fact that we live in society and execute our rights to walk, talk and otherwise interact with others in society we give tacit consent to police to investigate offences as it is in the public interest for them to do so, and that's their job whether some of us like it or not.