This is what you feel is right but I'm interested in what the law says and permits.
I think you could probably get a decent survey of at least what people are told at retail across different places. Most places do have some sort of citizen's arrest law. I know in Washington State in the US I was always told that you did have the right to essentially arrest and detain through at least some physical contact people you witnessed shoplifting. Managers could chase people down and potentially tackle them just by being told of a suspect. Brazen attitude lol.
A quick google suggested to me you'd really have to do some research to figure out exactly how far you can take it.
California is often a good example, and they allow anyone to detain someone until the Police arrives for up to (on a downward scale) and including "infractions." Allegedly according to wiki you could get detained by someone legally for a seat belt violation.
http://en.wikipedia.org/wiki/Citizen's_arrest
It's the kind of thing you are often best off actually looking for statutes and laws and trying to digest them. Like figuring out what kind of knife you can legally have in your car for utility purposes without committing a felony lol.