In the Uk anyone can make an arrest as long as they have witnessed the crime being commited and when they detain the person they read them thier rights, in this case Evilrip yes you could due to them selling copyright material which is classed as theft, I know this for a fact as I have done this quite a few times in my job

no police officer is needed to be present at the time of arrest or witnessing the crime in the UK anyway, I can't say for other countrys